Historic_Fort_Doors_2002_Assessment_0001.pdf

National Park Service U.S. Department of the Interior

Harpers Ferry Center Department of Conservation

Historic Fort Doors Condition Assessment Preservation Recommendations

Fort Pulaski National Monument

Historic Fort Doors

Harpers Ferry Center P.O. Box 50

Harpers Ferry WV 25425

Alan M. Levitan Conservator of Wooden Artifacts Department of Conservation 304 535 6702 U.S. Department of the Interior Washington, DC

Contents

Introduction 1 Goals of Treatment 2 Cost Estimate for Preservation Treatment 3

Sally Port Doors 3 Outer Doors 3 ^ Condition 4 '-^ Recommendation 9

Inner Doors (Sally Port Gates) 9 Condition W Recommendations 13

Entry Door North Bastion 14 Condition 14 Recommendations 7 7

Stair Tower Doors 17

Northwest Angle Stair Tower Door 19 Condition 19

East Angle Stair Tower Door 20 Condition 20

Southeast Angle Stair Tower Door 21 Condition 21

Stair Tower Doors 23 Recommendations 23

Appendix A Commercial Rust Converters: Surface Protection for Rusted Iron ;by Nancy E. Binnie Tannic Acid Treatment CO Notes Care and Cleaning of Iron, CCI Notes introduction The inner and outer pairs of sally port doors are original to the con struction of Fort Pulaski, completed in 1847. These doors histori cally provided the only ingress and egress to the fort and serve the same purpose today. Paint remnants on the doors appear to date to the period of historic usage.

Photographic images from the Civil War era, and from the mid - i930s ^ when administration of the historic fort was transferred to the National Park Service, provide a reasonably good record of the changing condition of the doors through the years. ^ v

The fort contains four other doors that park staff suspect may date to the original construction. These include the three stair tower doors and the door to the north bastion. My examination of the physical evidence, including hardware, fabrication techniques, and paint stratigraphy indicates that these doors are most likely contem porary to the sally port doors. Small wood samples were taken from all the doors and sent to the Forest Product Lab for identification.

All the samples were identified as southern yellow pine, providing additional reason to believe that the doors were fabricated and installed during the same period.

Some of the stair doors in a weathered condition are visible in pho tographs taken in 1935, prior to NPS restoration of the fort. This strongly suggests that they date to the construction of the fort rather than the 1930s restoration effort. Comparison of these doors with similar doors that were fabricated in the CCC restoration effort exhibit considerable difference in fabrication technique and hard ware.

For the most part, the doors are in relatively good condition consid ering their exposure to the elements for over 150 years and the fact that they have received little maintenance during much of that time.

Their condition is attributable to high quality materials and the fab rication techniques that were employed.

Photographs of the doors taken by NPS personnel in the 1930s indi cate that much of the deterioration seen today had occurred by that time. It is likely that the fungal decay at the lower portion of the outer sally port doors occurred when the moat was silted up. In one photograph of the outer sally port doors taken in 1935 the bottom portion of the doors appears darker, suggesting they had recently been in contact with mud or water, possibly the result of tidal action.

August 2002 Historic Fort Doors Condition Assessment 1

The primary factors affecting condition at this time are fungal dete rioration, erosion from sunlight and wind driven rain, and corrosion of ferrous hardware and its effect on adjacent wood surfaces. With preservation treatment and ongoing cyclic maintenance the doors can safely remain in place in the fort for the foreseeable future.

However no wooden artifacts can last forever when exposed to exterior conditions. A one-time preservation campaign can address the immediate condition problems, but to extend the outdoor exhibit life of the doors for as long as possible, an ongoing, cyclic monitoring and maintenance program will be necessary. Many of the preservation steps require re-treatment on a periodic basis.

Monitoring of condition can indicate how well the preservation , ^ treatment is holding up and suggest when repetition is required.

Given the relatively stable condition of the doors and the potential for damage inherent in removing them from their hinges, at this time I recommend that the objects be treated in place. It may however become necessary in the future to remove the doors for more complete treatment.

Goals of Treatment The primary goal of treatment should be to stabilize the doors and slow any future deterioration. Much of the damage and wear occurred during the period of historic use and therefore should be retained.

Restoration should be keep to a minimum, utilized primarily to repair damage that occurred after the period of historic usage. It is, for example, appropriate to tone in recent abrasions. This will improve the appearance of the doors and also indicate if new abra sions are occurring.

I do not recommend repainting the doors for the following reasons:

• Much of the historic paint film is well adhered to the substrate and continues to provide a measure of protection.

• Repainting will require the removal of some historic paint.

• Paint does not adhere well to weathered deteriorated surfaces.

• An application of fresh paint will require periodic scrapping and repainting.

• An intact paint film will preclude future applications of fungicide.

• New paint looks awkward on highly weathered wood surfaces from an aesthetic standpoint.

Instead I suggest leaving the historic paint exposed, consoUdating the paint where needed and applying clear water repellant with mildewcide and UV inhibitors to those surfaces where paint is lost.

August 2002 Historic Fort Doors Condition Assessment 2

Cost Estimate for Preservation Treatment Sally Port Doors: $ 1 6 , 8 0 0

North Bastion Door: $ 1 ,500 Stair Tower Doors:

Northeast Angle: $ 3 , 0 0 0

East Angle: $ 3 , 0 0 0

Southeast Angle: $ 6 , 0 0 0

Materials: $ 3 , 0 0 0

Sally Port Doors In describing the sally port doors reference is made to right and left when looking at the doors from the drawbridge. The side of the doors and gates facing the drawbridge is referred to as the exterior surface.

Outer Doors Each of the outer doors measures approximately 6 2 " wide by 1 2 0 " high. They are comprised of two layers of planks each 2 " thick. The outer layer consists of 12 vertical members while the inner layer has 23 horizontal members. Each plank is grooved and splined along the edges. The wood members are quarter sawn for strength and stabil ity. Wood samples from the doors were identified by the Forest Products Lab as being southern yellow pine, (pinus). Although the particular species of pine could not be identified, visual inspection suggests it is a long leaf pine which is characterized as heavy, strong, stiff, hard and moderately high in shock resistance.

The plank layers are joined together by means of ferrous rivets. The exte rior rivet heads are hemispherical with the exception of those along the top row and column closest to the hinge. These heads are flattened to enable the door to close tightly against the overlapping stone jamb.

Each door is hung on two large ferrous strap hinges that extend the full width. The hinges are affixed to the doors with bolts that have round heads on the exterior and square nuts on the interior. The irregular appearance of the projecting threads suggest they were made by hand.

The ferrous pintles are set into the

<*.*\d area

Pivoting Lock Bar

Wicket

Losses from fungal decay

Interior Sally Port Doors, 1937

August 2002 Historic Fort Doors Condition Assessment 3

Stone jambs. The lower pintle has an integral pin while the upper pintle has a loose pin secured by means of a wedged shaped key.

The lower hinge has a small oil hole above the pintle.

The doors are secured by means of a pivoting ferrous bar affixed to the right hand door. In the closed position the bar rests on two ferrous U brackets riveted to the left hand door.

A wicket, a small door for individual access, is cut into the left hand door. It swings on two strap hinges and is secured by a large sliding bolt. The wicket is constructed in the same manner as the larger doors and may have actu ally been cut out of the large door after its fabrication.

1'—

I

* *W A, Detail of wicket set in door, 1937

Condition: Outer Doors

• Surfaces are moderately soiled. There are scattered insect accre tions and nests.

• Approximately 6 0 % of the paint is lost from the exterior surfaces.

Most of the losses are on the lower portions of the doors.

• Approximately 15% of the paint is lost from the interior surfaces.

• Most of the paint remains well secured to the wood substrate.

There are some areas, generally on the edge of losses and adjacent to corroded ferrous hardware, where the paint is partially detached and in danger of flaking off entirely

• There are numerous abrasions, dents and scratches. Most appear to date to historic usage. Some appear to be more recent. The most obvious recent damage to both wood and ferrous surfaces is caused by the abrasion of the end of the locking bar as it is rotated to lock and unlock the doors. There are also abrasions on the exterior surface caused by use of the wicket.

• The exterior surfaces are weathered as a result of exposure to wind driven rain and sunlight. The weathering is more severe on the lower portions of both doors where exposure is greater. The wood surface is variegated as a result of the softer early wood eroding away at a more rapid rate than the denser late wood.

Although there is slow loss of wood fiber, the surface remains stable and there is little evidence of fungal deterioration with the exception of the bottom edge.

• The bottom edges of both doors are lost as a result of fungal decay.

The losses are somewhat irregular, averaging about 5 " wide. A portion of the lowest horizontal member is lost from the right hand door and the entire bottom horizontal member is lost from the left-hand door. The wood adjacent to these losses is some what deteriorated but the degree and extent of deterioration is not as great as might be expected. The lower two horizontal Unes of rivets are lost from the left-hand door. Only one of the lower rivets remains from the right hand door.

August 2002 Historic Fort Doors Condition Assessment 4

• Photographs of the doors dated 1935 show that the extent of loss at that time is about the same as seen today, indicating that the fungal deteriora tion occurred when the fort was aban doned and the moat silted in. The bottom of the doors and the floor appear wet in the photograph, sug gesting that mud had been removed from the doorway just before the image was taken.

• A series of square wood patches, or Dutchmen approximately 3 " x 3 " are mortised into the exterior surface of the doors beneath the heads of the bolts that secure the lower hinges.

These repairs could only have been executed when the bolts were removed from the hinges. The patches were probably necessary as a result of ferrous corrosion from the bolts dete riorating adjacent wood surfaces.

' Photographs dated 1935 show the wood patches in place suggesting the work was done in the period that the fort was functioning.

' Many of the patches are now split and deformed. Some are loose in their mortises and in danger of being lost entirely.

The lower portion of the left vertical member of the left hand door, extending approximately 4' from the bottom edge, is a replace-

Rust staining adjacent to rivet heads

Wicket

Relatively recent abrasions from locking/unlock ing the wicket

Patches beneath bolt heads

Lost rivets

Exterior Sally Port Door, left side

Paint remains only on upper surfaces, par tially protected from rain and sunlight.

Note wood losses along bottom edge.

Detail of abrasion on wood surfaces and rivet heads -interior left hand door

Detail of patch J, ^ on exterior sur- -'^ face of door, left side Details of old repairs and losses along bottom edge, left hand door

August 2002 Historic Fort Doors Condition Assessment 5 ment element. It is somewhat warped and twisted and has minor splits, but remains well affixed to the door. The patch appears weathered in a 1935 photograph, suggesting that it too was made in the period that the fort was functioning.

Exterior Sally Port Door, right side

Burnt area

Oil staining adjacent to hinge pintle

Abrasions from rotation of bar

Losses at bottom edge

Sheet metal covered boanj

Interior Sally Port Door, right side

August 2002 Historic Fort Doors Condition Assessment 6

• An irregularly shaped area, approximately i ' square, at the top of the right hand door is lost and the surrounding surfaces are charred. This damage is the result of a fire that spread through a portion of the gorge wall and ultimately through a slot in the brickwork. The damage appears in photographs from 1935. The charred surfaces are probably friable but could not be examined closely.

• The bottom edge of the wicket door is split away and lost.

• Boards wrapped with sheet metal have been affixed to the interior surfaces along the bottom edges of both doors. This repair was done to prevent pests from entering the fort through the opening along the bottom edges that was created by fungal decay. Park maintenance staff did the repair.

• The ferrous hardware is corroded to varying extents. In some instances the extent of the corrosion is great and has resulted in loss of material and strength as well as corrosion jacking.

Corrosion of the iron fittings has, in some cases, caused deteriora tion and splitting of adjacent wood members.

, Detail of corroded bolt, resuced to less than one-half its original diameter

August 2002 Historic Fort Doors Condition Assessment 7

• In general the extent of corrosion is greater on the exterior sur faces, particularly on those ferrous elements on the lower portion of the doors.

• The corrosion is active in some locations, characterized by orange corrosion product and the presence of moisture on the ferrous surfaces.

• On the interior surfaces there are remnants of coating on the hard ware and rivet heads that may be historic.

• There are remnants of black paint on the exterior rivet heads that appear to be from a later restoration campaign. The coating is on top of pitted and corroded iron surfaces.

Exterior sally port doors, 1935.

Note wet appearance of lower portion of doors and presence of water in entryway. Extent of fungal losses approximates that which is currently seen.

August 2002 Historic Fort Doors Condition Assessment 8

Recommendations

• Clean all surfaces by vacuum and/or compressed air. Mechanically remove mud dauber nests with wood scrapper/spatulas to avoid scratching underlying surfaces. Remove residue with cloth mois tened with water.

• Clean stable surfaces with odorless mineral spirits on clean, cotton cloths. Ensure that no paint is lost during cleaning process.

Ensure that wood surfaces do not snag cloth. For rough, uneven surfaces clean with mineral spirits using a soft bristle brush and blot solvent with cloth.

• Adhere splits with epoxy.

• Repair split, loose, and deformed old patches under bolt heads where possible. Re-adhere where necessary with low viscosity epoxy. Replace patches where necessary

• Apply consolidant to decayed and charred surfaces. (io% PVB in alcohol)

• Consolidate friable paint surfaces with B-72.

• Remove loose corrosion from ferrous surfaces with wire brushes and/or plastic abrasive pads. Ensure that adjacent wood surfaces are not abraded during process. Masking adjacent surfaces with Mylar or similar barrier film may be necessary.

• Make two apphcations of Rustoleum brand rust converter to cleaned ferrous surfaces. Ensure that no rust converter gets on adjacent wood surfaces. Application to bolt head should be done with small brush (no larger than Vi"). Masking wood surfaces may be necessary. Wait a least a day between apphcations. (see Appendix)

• Consider applying bumper to inner surfaces of ends of pivoting lock bar to prevent further abrasion. A hard rubber pad approxi mately 1/8" thick, affixed with double-sided tape should work well.

Any material will wear and require periodic replacement.

• Consider in-painting areas of recent abrasions to minimizing visual disruption and gauge the extent of future abrasion.

• Consider applying paraffin oil based water repellant/UV inhibitor to unpainted surfaces.

Inner Doors (Sally Port Gates) The inner doors or gates have diagonal latticework and arched tops.

The right hand door is latticed top and bottom, while the left hand door is latticed above and planked below the mid-rail. A wicket is set into the planked portion of the left hand door. The doors are approximately 4 " thick, 1 4 4 " tall and 5 4 " wide.

The lattice-work is comprised of four layers varying from 1-1/8" to 7 / 8 " thick. The layers are affixed to one another with flush rivets.

August 2002 Historic Fort Doors Condition Assessment 9 screws and cut nails and set into grooves on the inner edges of the rails and stiles.

The doors are hung on hinges similar to those found on the outer doors and are affixed with round head bolts and square nuts. They are secured with a bar that pivots on the right hand door and rests in two U shaped brackets on the left hand door.

Inner Sally Port Door Interior View

Condition of Inner Doors

• Only the interior surfaces of both doors are visible. The outer sur faces are not currently accessible because the hinges are frozen in the open position.

• The surfaces are soiled. There are scattered accretions from insect activity such as mud dauber nests, spider webs and cockroach droppings.

• Approximately 4 0 % of the paint is lost from the exposed (interior) surfaces. Most of the losses are on the lower portions of the doors.

• Most of the paint remains well secured to the wood substrate.

There are some areas, generally on the edge of losses and adjacent to corroded ferrous hardware, where the paint is partially detached and in danger of flaking off entirely

August 2002 Historic Fort Doors Condition Assessment 10

Damage from 1862 siege

Splitting/losses along inner edge of hinge stile losses on bottom of hinge stile

Interior surface, left hand door

Split ferrous hinge pi

Door currently wedged in place against brick ceiling

Splitting adjacent to bolt head:

Extensive corrosion and losses on U bracket

Powder post beetle damage on latticework

Lost elements from latticework Splits/losses on inner edge of hinge stile

Splits in lower rail adjacent to bolt heads

August 2002 Historic Fort Doors Condition Assessment 11

Details of splits/losses of hinge stile

• There are numerous abrasions, dents and scratches. Most appear to date to historic usage. Some appear to be more recent.

• There is old damage to the left-hand door that is thought to have occurred during the siege of 1862. This damage, which resulted in the loss and splitting of sections of the arched stile and lattice, is seen in images taken in 1937.

• The lower portion of the hinge stile on the left hand door is damaged. The outer and middle layers have sustained losses.

There are a number of splits, some of which are unstable and likely to increase in length with the possibility of splitting off entirely.

• The upper mid rail on the left side is split. This damage appears old and may date to the seige.

• There is evidence of insect infestation on the lattice work, lower rail and lower stile of the right hand door. The damage, which includes larval tunneling and exit holes, appears to have been done by powder post beetles. The infestation does not appear to be active at this time.

• There appears to be old termite damage on the left hand door in the stile adjacent to the wicket.

• Two small sections of the lattice work are missing from the right hand door.

• Some of the plaster-like fills over the screw-holes have fallen out. It is not clear whether the screws are original to the fabrication of the doors or early repairs.

• The inner edges of both hinge stiles are worn and split away. This damage is probably the result of the doors binding on the stone jambs.

• The ferrous hardware is, for the most part, heavily corroded. There is extensive pitting and loss. The extent of the corrosion is proba bly due to past water leaks, the effects of which are also evident on the stone jamb.

• The upper hinge on the right side door is particularly corroded.

August 2002 Historic Fort Doors Condition Assessment 12

Detail of extensive corrosion and losses to U bracket on right hand door

Fills over screw heads have fallen out

I f

The hinge pin has split as a result of corrosion jacking of the key.

• Two bolts are missing from the lower wicket hinge. One bolt and one nut are missing from the upper wicket hinge.

• There are small areas on the ferrous hardware which retain rem nants of black paint.

Recommendations:

• Remove wedges and attempt to free hinges by repeated application of lubricant/rust remover followed by gentle pressure on the door rails. Do not force doors to move as this could damage rails. Blot up excess lubricant to prevent further staining of adjacent wood or masonry surfaces. Localized heating of the hinges may ulti mately be necessary to free them.

• Once hinges are free, outer surfaces of doors can be examined. It is likely that damage similar to that seen on the inner surfaces will be found. However it is possible that more extensive insect or fungal deterioration may exist.

• Clean all surfaces by vacuum and/or compressed air.

• Clean stable surfaces with odorless mineral spirits on clean, cotton cloths. Ensure that no paint is lost during cleaning process.

Ensure that wood surfaces do not snag cloth. For rough, uneven surfaces clean with mineral spirits on soft bristle brush and blot solvent with cloth.

• Adhere splits with epoxy.

• Apply consoUdant to decayed surfaces and areas degraded by insect infestation. (io% PVB in alcohol)

• Consolidate friable paint surfaces with B-72.

• Remove loose corrosion from ferrous surfaces with wire brushes and/or plastic abrasive pads. Ensure that adjacent wood surfaces are not abraded during process. Masking adjacent surfaces with

August 2002 Historic Fort D(x>rs Condition Assessment 13

Mylar or similar barrier film may be necessary.

• Make two applications of Rustoleum brand rust converter to cleaned ferrous surfaces. Ensure that no rust converter gets on adjacent wood surfaces. Application to bolt head should be done with small brush (no larger than Vi"). Masking wood surfaces may be necessary. Wait a least a day between apphcations.

• If this pair of doors is to be closed and locked on a regular basis, consider applying a bumper to the inner surfaces of the ends of the pivoting lock bar to prevent further abrasion. A hard rubber ^ pad approximately i/8" thick, affixed with double-sided tape should work well. Any material will wear and require periodic replacement. , v

• Consider in-painting areas of recent abrasions to minimizing visual disruption and determine extent of future abrasions.

• Consider applying paraffin oil based water repellant/UV inhibitor to unpainted surfaces.

Entry Door North Bastion In describing the north bastion door reference to right and left is made looking at the door in the closed position from the parade ground. The exterior surface is considered to be the side of the door facing the parade ground when in the closed position.

The door is comprised of four vertical boards, affixed with clinched nails to 3 horizontal battens on the interior surface. The upper and lower battens are also affixed by means of flush head rivets that extend through to the two strap hinges on the exterior surface. The top of the door is curved to conform to the arched ceiling of the bastion. A curved batten extends from the upper edge of the top batten to the hinge edge of the door. Two gun slots are cut into the upper portion of the door in the center of each of the inner vertical members.

In recent years the door has been permanently affixed to the brick wall in the open position by means of a bolt that extends through the door into an anchor in the brick. The bottom edge of the door rests directiy on the brick floor.

Condition

• The surfaces are soiled.

• There are accretions from insect activity including mud dauber nests, spider webs and various cocoons. Most of the insect accre tions are on the exterior surface, which has been immediately adjacent to the brick wall.

August 2002 Historic Fort Doors Condition Assessment 14

Note staining on wood surfaces from corroded ferrous

• Paint remains on approximately 3 0 % hardware

August 2002 Historic Fort Doors Condition Assessment 15 of the interior surface, which is exposed to wind driven rain and light when in the open position.

• Paint remains on approximately 7 0 % of the exterior surface, which is protected from wind driven rain and light when in the open position.

• A chip, approximately 18" long is missing from the edge of the outer vertical member. Other portions of the outer edge have sustained minor chipping, abrasions, and losses.

• There is extensive chipping and splitting along the bottom edge.

This has probably occurred because the door scrapes on the brick floor when it swings due to sagging of the hinges. Some of the splits are unstable and will likely result in further losses if not adhered.

• Moisture is wicking up through the masonry floor into the end grain of the vertical members of the door. This has resulted in fungal staining, tide lines and incipient decay. Organic debris has accumulated at floor level between the door and the brick wall, accelerating fungal deterioration.

Detail of bottom edge, interior surface of door Detail of bottom, exterior surface of door Note chipping, splitting and fungal staining. There is extensive There is water staining along the bottom edge and extensive cor-corrosion on rivet heads and staining and splitting of adjacent rosion pitting of the strap hinge, wood surfaces.

Many of the ferrous rivets and nail heads are heavily corroded, causing staining and deterioration of adjacent wood surfaces. • M W * ' '^MMi ^ Corrosion jacking has caused some of the ferrous elements to split "'W^^^^IRJS'̂ wWi^W adjacent wood fiber. - »; -^p^ 1

A rivet head is lost from the lower batten as a result of corrosion. ' --.f^ The strap hinges are heavily corroded. Black paint on the hinges, pL'r̂ i*: - - ^ which may date to historic fort usage, is cupping and actively '"JP"**"*'^"' ' T™"'*' " flaking. •

The moisture content taken in various locations on the door is Tĥ erê il art!ve c°orros?on,*F̂ ^̂ ^̂ about 13%. The moisture content does not vary substantially from "^'''"^ p '̂"*-top to bottom.

August 2002 Historic Fort Doors Condition Assessment 16

Recommendations

• Clean all surfaces with vacuum and/or compressed air at low pres sure.

• Clean stable surfaces with odorless mineral spirits on clean, cotton cloths. Ensure that no paint is lost during cleaning process.

Ensure that wood surfaces do not snag cloth. For rough, uneven surfaces clean with mineral spirits on soft bristle brush and blot solvent with cloth.

• Remove fungal staining.

• Apply BoraCare to unpainted surfaces on lower portion of doors.

Attempt to get BoraCare to wick up bottom end grain surfaces.

• Apply PVB (io% solution in alcohol) to fungal deteriorated sur faces.

• Adhere unstable splits with low viscosity epoxy.

• Remove flaking paint from hinges.

• Remove active corrosion from all ferrous surfaces.

• Apply Rustoleum rust converter to ferrous surfaces, (see Appendix)

• Attempt to shim up door hinges to lift the bottom edge of door above masonry floor. If this does not prove possible, slide mois ture barrier such as sheet lead between bottom of door and floor.

An L shaped barrier, with one leg placed against the brick wall, is likely to stay in place without the need to permanently attach it to the door.

Stair Tower Doors In describing the stair tower doors reference to right and left is made looking at the doors from the parade ground. The side facing the parade ground is referred to as the exterior surface.

The three stair tower doors are fabricated in the same manner. Like the other original fort door, all the stair tower doors are made from southern yellow pine. They are comprised of two layers of tongue and groove planks. The outer layer has lo vertical elements and the inner layer has 8 horizontal elements. The layers are joined with round head nails, set flush on the exterior surface and clinched over on the interior surface.

Each door swings on two strap hinges. The lower hinge is set on a pintle with an integral pin; the upper hinge has a loose pin secured with a key. Hemispherical head bolts with square nuts affix the hinges to the doors.

The presence of a keyhole, as well as wear and tool marks indicates that a surface lock was originally affixed to the interior of each door.

August 2002 Historic Fort Doors Condition Assessment 17

Stair Tower Door, 1935

Northwest Angle Stair Tower Door

August 2002 Historic Fort Doors Condition Assessment 18

Condition

• The surfaces are moderately soiled.

• Bottom edge of lowest horizontal member is lost.

• There is splitting and losses on the outer edges of the vertical members on both sides of the door. The damage is greatest on the lower portions of the door.

• The lower portion of the exterior surface on the hinge side is head member in of interior member

Detail of lower exterior surface , , ^ . , dented. This appears to be done with a prying or propping tool and may date to historic usage of the fort.

• About io% of the paint is retained on the exterior surface. The paint remnants are on the upper surface of the door that is shaded from direct sunlight.

• About 65% of the paint is retained on the interior surface. Most of the losses are on the lower surfaces and on the lock side of the door where paint has worn away.

August 2002 Historic Fort Doors Condition Assessment 19 and subject to direct sunlight are weathered. The surface is some what rough and variegated as a result of the early wood eroding more rapidly than denser late wood.

• The nail heads, hinges and bolts are corroded. In some locations the corrosion is extensive and there is substantial pitting.

East Angle Stair Tower Door

Condition

• The surfaces are moderately soiled.

• The bottom edge of the lowest horizontal member is lost, probably the result of fungal deterioration. Losses and splitting on vertical members extend up approximately 4".

• There is splitting and losses on the outer edges of the vertical members on both sides of the door. The damage is greatest on the lower portions of the door.

Patches under bolt heads

Losses from fungal decay

Exterior, East Angle Door

August 2002 Historic Fort Doors Condition Assessment 20

• There is a series of square patches mortised into the exterior surface beneath the bolts that affix the lower strap hinge. These patches are similar in size and fabrication to those on the sally port doors, which are seen on a photograph taken in 1935. Seven patches are now split, deformed and loose in their mortises. There is likelihood that some will be lost if not repaired.

Detail of patches on exterior surface

Original location of lock on inte rior surface

• The lower portion of the exterior surface on the hinge side is dented. These marks are similar to those found on the other two stair tower doors. It appears to have been done with a prying or propping tool and may date to historic usage of the fort.

• About 15% of the paint is retained on the exterior surface. The paint remnants are on the upper surface of the door that is shaded from direct sunlight.

• About 4 0 % of the paint is retained on the interior surface. Most of the losses are on the lower surfaces and on the lock side of the door where paint has been worn away.

• The paint stratigraphy matches that found on the other stair tower doors.

Southeast Angle Stair Tower Door

Condition This is the most deteriorated of the doors and requires treatment in the near term to avoid further damage.

• The surfaces are moderately soiled.

• There is widespread light green fungal staining on the exterior

August 2002 Historic Fort Doors Condition Assessment 21 surface. This side of the fort is subject to less direct sunlight than the other facades.

• Approximately 5 0 % of the lowest horizontal member is lost, proba bly the result of fungal deterioration. The remainder is deterio rated and subject to further losses.

• In places, the losses and splitting on vertical members extend up approximately 8" from the bottom edge.

• There is a large area of fungal loss and decay that extends down from the top edge. This has primarily affected the vertical plank that is the second in from the outside. The interior horizontal planks are also deteriorated to a somewhat lesser extent. The damage appears to have occurred as the result of a long term water leak from above that dripped down through the masonry while the door was in the closed position. The wood members in this area are unstable and likely to sustain further damage if not repaired. There appears to be carpenter ant damage in the deteri orated area. The insect infestation does not appear to be active.

• There is a series of square patches mortised into the exterior surface beneath the bolts that affix the lower strap hinge. These patches are similar in size and fabrication to those on the sally port doors and the east angle door. Some of the patches are now split, deformed and loose in their mortises. There is likelihood that they will be lost if not repaired.

Detail of fungal deterioration and losses at upper end of door

Rust staining

Lost patch and bolt

Loose patch

Detail of deterioration at lower edge of door

August 2002 Historic Fort Doors Condition Assessment 22

• The vertical member on the hinge side sustains a split that extends approximately 3 feet up from the bottom.

• The lower portion of the exterior surface on the hinge side has numerous dents. These marks are similar to those found on the other two stair tower doors. It appears to have been done with a prying or propping tool and may date to historic usage of the fort.

• About 5% of the paint is retained on the exterior surface. The paint remnants are on the upper surface of the door that is shaded from direct sunlight.

• About 3 0 % of the paint is retained on the interior surface. Most of the losses are on the lower surfaces and on the lock side of the door where paint has been worn away.

• The paint stratigraphy matches that found on the other stair tower doors.

• There is extensive, active corrosion on the hinges, bolts and nails.

Rusted ferrous elements have stained adjacent wood surfaces. In places corrosion jacking of ferrous elements have caused splitting and loss of wood fiber. Some of the bolts along the lower edge are lost.

Stair Tower Doors

Recommendations

• Clean with vacuum and/or compressed air.

• Clean stable surfaces with odorless mineral spirits on clean, cotton cloths. Ensure that no paint is lost during cleaning process.

Ensure that wood surfaces do not snag cloth. Cloths cannot be used on the more deteriorated and rougher surfaces. Use soft bristle brushes to apply mineral spirits and blot excess with cloth.

• Remove fungal staining. (SE Stair tower)

• Apply BoraCare to unpainted surfaces on lower portion of doors.

Attempt to get BoraCare to wick up bottom end grain surfaces.

August 2002 Historic Fort Doors Condition Assessment 23

• Apply PVB (io% solution in alcohol) to fungal deteriorated sur faces. Highly deteriorated surfaces may require additional apph cations of higher solution consolidant.

• Adhere unstable splits with low viscosity epoxy.

• Insert blocks as needed to stabilize decayed area. (SE stairtower)

• Remove flaking paint from hinges.

• Remove active corrosion from all ferrous surfaces.

• Apply Rustoleum rust converter to ferrous surfaces, (see Appendix)

August 2002 Historic Fort Doors Condition Assessment 24

Appendix

August 2002 Historic Fort Doors Condition Assessment 25

CCI-ICC On-Going Research - Rust Converters Page 1 of 2 laciiaii Con ser\"atioii. Itistitiite- Researcii Project m

Commercial Rust Converters: Surface Protection for Rusted Iron by Nancy E. Binnie

Between 1987 and 1992, researchers in CCI's Conservation Processes Research Division investigated the durability of nine commercial rust converters. This was done at the request of several agricultural and industrial museums across Canada that have been experiencing problems with msting in iron artifacts that are exhibited or stored outdoors.

ferric tannate) and a polymer (which consolidates the corroded surface).

For CCI's investigation, nine rust converters were obtained from a variety of sources. Mild steel plates were selected for use as the test surfaces because many agricultural and industrial machines employ this material. The plates were air-abraded, were placed outside for two to three months to rust, and then were coated with the rust converters. They were not given any additional coats of paint before testing.

Outdoor exposure tests were carried out for five years at three locations across Canada: on the rooftop of the Maritime Museum of the Adantic in Halifax, in the back parking lot behind tlie CCI building in Ottawa, and in the middle of a hay field at the Ukrainian Cultural Heritage Village near Edmonton. The annual precipitation, the mean monthly temperature, and the amount of bright sunshine varies considerably in each location. The ageing properties of the coatings were rated semi-annually. Ratings included evaluating any changes to the surface of the metal.

A "30-day salt spray test" was carried out on a separate set of plates that had been coated with the rust converter.

Before the plates were coated, corrosion products on the rusted plates were analyzed in the Analytical

In industry, the paint-like primers are applied directly to rust-covered iron surfaces after only minimal surface preparation. Usually, paint is then applied over the surface that has been treated with a rust converter. The manufacturers state that the rust converter wi l l stabilize corroded surfaces without the need to remove the rust. Rust converters thus offer an alternative to the approach used for conventional metal primers, where a corroded surface must first be abraded down to-bare metal. A typical formulation contains tannic acid (which reacts with the rust to form a blue/black

5/15/97 2:24:20 PM

CCI-ICC On-Going Research - Rust Converters Page 2 of 2

Research Services Division at CCI using x-ray diffraction. It was found that the rust on the plates exposed in Ottawa and Edmonton was mainly composed of lepidocrocite (garama-FeOOH), whereas the rust on the plates from Halifax was mainly magnetite (Fe304) with only minor amounts of lepidocrocite.

After the results from the outdoor and salt spray testing were analyzed, three rust converters were found to have useful properties: Conquest (available from National Chemsearch, Brampton), Rust-Oleum Rust Convert (available from Rust-Oleum Canada, Downsview), and Neutra Rust (purchased at the time from Bernard Marks Company Ltd, Toronto, but no longer available from , this distributor). ' ^

In general, rust converters are more expensive than paint. When used without a top-coat of paint, the rust converters gave approximately two years of protection from further rusting. After two yeai-s of exposure, the surfaces began to deteriorate and the rust became active. In the marine chmate of Halifax, the rust deteriorated more quickly than at Ottawa or Edmonton.

For museum artifacts, it is often inappropriate to remove corrosion products when cleaning.

However, inadequate surface preparation is often identified as a primary cause of paint adhesion failure, and most conventional paints do not adhere well to rusted surfaces. Applying a conventional, compatible, long-lived protective paint onto the primer should further enhance the protection of the metal surface, although this was not investigated in this project.

It is hoped that conservators will make use of the long-lasting rust converters identified in this study as primers for corroded iron surfaces. Further work is planned which wil l investigate the effect of rust converters coated with various paints. Staff involved in this project at CCI included Mark Gilberg, Deborah Rennie-Bisaillion, Lyndsie Selwyn, Carl Schhchting, Bob Barclay, and Nancy Binnie.

5/15/97 2:24:28 PM

Communications Canada

Canadian Conservation institute

CCI Notes

Institut canadien de conservation

9/5

Tannic Acid Treatment

Introduction Iron objects are often covered with a layer of corrosion, which can vary from a light rust film to heavy, dis figuring scale. Corrosion is un desirable when it detracts from an object's appearance and usefulness for display. Also, because iron rarely corrodes in an even, regular manner, the corrosion layers formed are not as protective on iron as are corrosion layers forming on other metals (CCI Note no. 9/1, Recognizing Active Cor rosion).

Uneven corrosion permits the penetra tion of water vapour and oxygen, which react with underlying metal.

Protective coatings such as waxes and lacquers can be applied to metal objects to reduce the transmission of water vapour and oxygen. However, if coatings are applied to porous cor rosion layers, they may be very dif ficult to remove at a later date, should the object begin to actively corrode.

Tannic acid on the other hand, is a preferable coating for iron because it can be applied both to heavily cor roded and lightly corroded iron to en hance the protective qualities of these corrosion layers. Also, tannic acid can be removed. Tannic acid is a complex organic acid found in most plants. Individual products are usual ly identified by the species of plant from which they come. When ap plied to iron, tannic acid reacts with the iron to form ferric tannate, a protective blue-black film whose quality can be controlled to some ex tent by the method of application.

This coating will inhibit the most sus ceptible areas from reacting with water vapour, in the short term. It will also enhance the appearance of an object by producing a uniform finish.

However, it is important to remem ber that the application of tannic acid will not eliminate the need for en vironmental controls, nor will it remove damaging soluble salts from actively corroding objects (CCI Note

no. 9/6, Care and Cleaning of Iron).

Preparing the Iron Prior to applying tannic acid to iron, the surfaces should be free of surface dirt, extraneous accretions, oils, and grease (CCI Note no. 9/6, Care and Cleaning of Iron). Ideally, composite objects should be dismantled. If this cannot be done, care must be taken to ensure that, during application of tan nic acid, none of the acid touches material other than the iron. Irrever sible staining may result, especially on proteinaceous materials such as wool, silk, leather, bone, horn or ivory.

1030 Innes Ottawa, Canada K1A 0C3

(613) 998-3721

It is not necessary or desirable to remove light rust films or heavy cor rosion prior to application of tannic acid.

Preparing the Acid Solution Tannic acid is a light, fluffy powder.

Its colour varies from brown to gold en brown, depending on the grade and the manufacturer. Because a fixed, uniform formula for tannic acid does not exist, there is consider able variation in quality among avail able brands. At C C I , tests carried out on grades from various manufac turers have found that the brand \aelding the most consistent and pre dictable results is produced by B D H Chemicals, at a reasonable price.

Any concentrated chemical poses a potential health hazard. Care must be taken not to inhale the powder or bring the acid in contact with the skin. A dust mask should be worn when weighing and mixing the dry powder. For convenience, it is recom mended that a 10% solution be prepared; this can be refrigerated and portions used or diluted as needed.

Recipe for one litre of 10% solution of tannic acid 100 grams tannic acid deionized or distilled water ' •

(about 900 ml) 50 ml ethanol approx 2 ml of dilute phosphoric acid (H3PO4), if available

Notes on the ingredients:

Tannic acid is very light; a 100-gram measure is bulky. A mixing vessel holding at least 1.5 to

2.0 litres is required.

Use deionized or distilled water;

tap water may contain chlorine and other dissolved salts, which should not be introduced to iron.

Ethanol acts as a wetting agent that will enhance the flow of the solution into p>orous corrosion layers and into all the fissures of a corroded iron surface.

Phosphoric acid lowers the p H of the acid solution, and increases the amount of iron available for reac tion with tannic acid. It is not necessary to be concerned about residues of the acid remaining on the iron, since phosphoric acid will react with iron to form ferric phosphate, which protects iron.

So little acid is introduced in this method that there is no danger of excess amounts crystallizing on the surface.

Equipment

- balance

- mixing container (glass), at least

1.5 litre, that can be heated

- scoop and stirring spoon or rod

- eye dropper

- p H papers

- measure in mis

(i.e., graduated cylinder)

Mixing the solution Measure and mix 800 ml of water and the 50 ml of ethanol in a glass or high-quality stainless steel container.

Plastic containers should not be used because they cannot be heated.

Wearing gloves and a dust mask, weigh the tannic acid. If your museum does not have a balance, a school science lab may be able to lend one.

Add the acid to the water/ethanol solution gradually, stirring constant

ly. To accelerate the process, gently heat the solution on a hot plate.

When the tannic acid has dissolved, add enough water (approximately another 100 ml) to make a total volume of 1 litre.

Prepare a dilute phosphoric acid solu tion by pouring 9 ml of distilled or deionized water into a glass container and adding 1 ml of concentrated phosphoric add, usually sold in an 857o concentration. Always add acid to water, rather than vise versa, in order to avoid violent reactions.

If the p H of the tannic acid solution exceeds 2.4, it will be necessary to lower the pH by adding dilute phos phoric acid. With the aid of a drop per, add the dilute phosphoric acid prepared above, stirring continuous

ly. After adding about 10 drops, test the pH again. Continue until the pH reaches 2.2 to 2.4, a concentration that may require about 2 ml, or 50 drops.

PH2 .2 -2 .4

range for tannic acid sol.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 add neutral alkaline

As solution becomes more acidic, pH drops.

CCI Notes 9/5 of the dilute phosphoric acid, depend ing on the initial pH of the tannic acid.

Store the tannic acid solution in a labelled, sealed container, preferably in a refrigerator. The label should bear the solution strength, composi tion, pH, date of preparation, name of the person who prepared it, handling precautions (gloves, protective cloth ing), and disposal instructions (pour down drain with ample water).

Dilution of Tannic Acid Stock To achieve an even coating of ferric tannate, it is best to apply several coats of a dilute solution of tannic acid rather than one concentrated coat. Ten percent tannic acid, as prepared above, is too concentrated to produce a good result. For most purposes, it should be diluted from 2% to 3%.

A simple method of dilution is to mix the 10% solution 50/50 with deionized water, thereby yielding a 5% solution. If desired, this 5% solu tion can then be diluted 50/50 again with deionized water, yielding a 2.5% solution.

Test the p H after dilution and add more drops of phosphoric acid if necessary until the p H is again in the range of 2.2 to 2.4.

Applying the Tannic Acid Prepare a working space, preferably a table, covered with absorbent paper towelling or plastic, and free of ex traneous objects. Two stiff bristle brushes, such as tooth brushes, are re quired: one with which to apply the acid and one with which to brush the object after the acid has dried. As this procedure can be messy, ensure that the acid will not splatter surfaces that it could stain (e.g., wood, cloth ing). In good weather, the procedure could be performed out-of-doors.

Protective clothing (gloves and a full apron) are advised. If eyeglasses are not worn, safety glasses or goggles should be.

Once a 2.5% solution of tannic acid has been prepared, brush it onto the object. To accelerate the reaction be tween the acid and iron, heat the acid to approximately 50 °C before applica tion.

Continue brushing as the acid dries to distribute the solution evenly and to introduce oxygen, which will produce an even colour.

Discolouration will develop quickly, usually beginning in pitted areas. As these areas become coated with an even, coherent film of ferric tannate, they resist further reaction, and the tannic acid will begin to react with less corroded areas. The presence of phosphoric acid assists in establishing an even reaction over the surface.

Once the first coat has dried, the sur face of the iron should be brushed with a stiff, dry brush to remove flaky areas of ferric tannate. Another coat of tannic acid should then be ap plied, still brushing as the acid dries.

These steps should be repeated until a coating of the desired density and colour is achieved.

When the tannic acid in the container becomes black, it should be discarded and replaced with fresh solution.

When dealing with case-hardened ob jects and steels such as cutting tools, it may be found that the tannic acid/iron reaction is different around the working edges. Also, if there are welds or joins, a different appearance in the ferric tannate should be ex pected at these points. Heavy cor rosion layers on objects will take longer to react than will light rust or bare metal.

Some practice may be necessary to be come familiar with the ferric tannate film and how its formation can be controlled. By increasing the con centration of tannic acid to 2.5% to 5%, a much darker, thicker film can be achieved.