Alburnam's Archive

Ó 2000-2001  Stephen A. Shepherd

Treating Teak

Because of the large number of inquiries I have decided to write an article about the treatment of teak in furniture and woodwork for either interior or for exterior applications.  Teak (Tectona grandis) a native of India, Burma (What ever it is called today), Siam (Thailand) and Java has been used for centuries as an excellent shipbuilding wood because of its unusual strength for its weight, legendary durability and how well it stands up to weather.  Filled with silica and other minerals it is tough on edge tools dulling them quickly.  Teak contains natural oils, which not only make the wood more durable; it also fills the sandpaper quickly.  Teak seasons very slowly but is extremely stable once it is completely dry.  Teak ranges in color from light honey to warm brown with darker brown streaks that can be straight grained or mottled and all teak darkens somewhat with exposure.  In order to maintain the natural color, teak needs an oil finish or an oil/varnish finish to prevent the wood from graying from exposure.

Because of the durability and strength, teak is a popular wood for exterior applications such as outdoor furniture and woodwork.  In order to maintain the new look the furniture or woodwork needs to be protected from exposure to ultra-violet radiation and water if possible.  If the furniture can be placed in a shaded area that is protected from rain it will last longer.  In the wintertime, the furniture should be covered to protect it from sun and weather.  Also do this if the outdoor furniture is not going to be used for an extended period of time.  Putting small wooden blocks under the legs of furniture that spends the winter in the snow or rain will help prevent the wood from taking up water hastening the deterioration process.  During the construction process of outdoor furniture it is preferable to place the wood that comes in contact with the ground such as chair or table legs, upside-down from how it grows in nature.  All wood has cells that contain little one-way valves that through capillary and expiration action draws water up the tree.  By placing the wood upside-down from how it grows reverses the valves and inhibits water take-up.  Water will still soak up into the fibers, so make sure the feet or parts that touch the ground are treated with oil or oil and varnish.

As unfinished teak ages it turns a silvery gray color and with increased age the surface slowly begins to break down and becomes fuzzy, but this takes some time.  If the teak has just turned gray, applying Moses T’s Reviver can easily renew it.  You can test if the wood will turn back to its natural color by getting it wet with water, if it goes back, that is the color it will be after the Reviver.  If it stays a light gray color they you will need to sand the surfaces slightly to get back to undamaged wood.  You must also do any repairs to the teak before any consolidation or finish work is done to insure that the oil or finish does not interfere with the glue.

When unfinished or untreated teak is exposed to the weather, the natural oils will eventually wash off, the lignin is eroded and the cellulose fibers are all that remains and this is the fuzzing that occurs on weathered teak.  Because of the surface breakdown, the fibers must be consolidated and this is best done with a penetrating oil treatment like Reviver.  The loose surface fibers can be removed by lightly sanding to remove the fuzz before the oil is applied.  The surface of the wood needs to be properly prepared before any treatment, which includes cleaning and washing the surface to remove loose debris.  After it is completely dry it should be sanded to smooth and remove any surface fuzz that might be left on the teak.  Small surface cracks or checks will start to close up with the first application of Moses T’s Reviver.  Very dry wood will require several treatments of the Reviver in order to consolidate the fibers deep within the wood.  After applying the Reviver, allowing it to soak in and wiping off the excess, it is a good idea to check back after 30 minutes or so and check for ‘bleed out’ where a little oil will come back out the wood to the surface.  This is caused by the dry wood fibers taking up the Reviver causing the cells to swell up and can squeeze some oil out to the surface.  Just wipe off the oil and allow the wood to dry.  This might happen after any coat you apply as the oil fills and consolidates the wood fibers of the teak.  The oil needs to dry overnight before the next application to assure that the early coats that are deep within the wood will dry.  After the teak has been treated with Revive it needs to be treated with Moses T’s St. John’s Oil for a satin finish or Moses T’s St. John’s Wax for a wax sheen and additional protection from water damage.  These oil finishes will need to be re-applied every year or two depending upon the exposure and use.  This also works on other exposed woods besides teak.

Another excellent finish for teak is exterior marine spar varnish such as McCloskey’s Man-O-War™.  If the wood is badly damaged I will follow the above procedure to consolidate and prepare the teak for a varnish finish.  If the teak is new, I will treat it with Moses T’s St. John’s Oil, wipe off any excess and allow to dry for at least 24 hours.  The Oil will bring out the grain and prepare the teak for the spar varnish film finish.  After the oil is dried it is lightly sanded with 220 grit and the surface cleaned with a tack cloth.  I then thin the spar varnish with 10 to 15% turpentine and wipe or brush it on the surface in a dust free environment.  After it has dried overnight, lightly sand with 220 grit sandpaper, tack the surface and apply another application.  I repeat until I have 3 or 4 coats or until I reach the desired results.  Spar varnish is slightly flexible and will adjust to some movement of the wood as it is exposed to changes in the temperature and humidity.  You will have to renew the spar varnish every 4 or 5 years depending upon exposure.  Check your wood every year to determine if it is time to redo the finish.  By constantly monitoring the condition of the wood you will detect the beginning of any breakdown in the finish before it becomes a big problem.

These treatments need to be applied to all surfaces including the underside of table tops, the underside of chair seats.  Finishing only one side of any wood will cause problems from unequal exposure to temperature and humidity.  Maintain the balance by finishing all exposed surfaces.

Another interesting use of teak is that it can be bleached and stained to look like walnut.  Conversely you can bleach walnut and stain it to look like teak.  I discovered this when I purchased an eighteenth century reproduction blunderbuss made in India.  The stock was made of teak and originals would have had a walnut or maple gunstock.  I bleached the teak, stained it with burnt umber in oil and it looked just like walnut.  The second I ran across when repairing a contemporary Scandinavian dining room table of 'teak'.  The veneer on the top edge was damaged and when making the repair I discovered it was walnut that had been bleached and then stained a teak color.

Gluing new teak can present a problem like all oily exotics and I will discuss the two current schools of thought.  There are those who insist on wiping the joints with a solvent such as acetone or alcohol to clean off the oils to prepare the surface for gluing.  Then there are those that insist that wiping the oily wood with a solvent will draw more oils to the surface, actually weakening the glue joint.  After much consideration and experimentation, I have to matriculate in the latter institution and no longer use solvents on oily woods at the glue joints.  The best preparation of a glue joint is keying or toothing, which is always a good idea.  A traditional method of preparing oily woods or even metal such as brass for gluing is to etch it with a clove of garlic.  A fresh clove of garlic is cut and the cut end rubbed on the area to be glued.  Any garlic debris is brushed off the joint and it is ready for glue.  This cleans the gluing surface without drawing up any more oil from these exotic woods.  See Using Hide Glue.

In 1994 we built and installed a U-shaped teak countertop with a French sink, the countertop sits on top of the sink and surrounds it on 3 sides.  The 1 ½ inch square pieces of teak were machined at the shop and were installed piece by piece in place.  Using modern waterproof glue the pieces were screwed together with stainless steel screws.  The last screw holes were plugged with teak plugs and the surface scraped and sanded smooth.  It was then finished with pure almond oil.  The countertop is used every day and subject to constant contact with water.  The homeowner wipes it down once a week with almond oil, and it looks as good today as it did the day it was installed.

Always dispose of oily rags properly.  Place them in water and then in an airy location (outside) where they can air dry.  A pile of oily rags can spontaneously combust and cause a fire, so always dispose of oily rags properly.

For Moses T's St. John's Oil and Moses T's St. John's Wax see Product Line

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General Repairs

Burl bowl showing repair and touchup

While repairing and restoring furniture you will always encounter problems that you have never seen before and probably won’t see again.  There are certain types of repairs that can be used on many different pieces with similar damage.  Restoration work is an on-going learning process and be prepared to get new lessons constantly.  Repairs are best done as soon after the damage occurs as possible, so that all of the breaks are fresh and crisp.  These makes the repairs easier to do, are less visible and require the least amount of finish touch up work.

Loose joints are the result of glue failure, wood movement or abuse.  There are two basic types of joints: edge joints such as table tops and panels and angle joints such as mortice and tenon or dovetail joints.  While there are many more joints they are usually with two boards at 180º (edge joint) or two boards at 90º to each other (angle joints).

Simple glue failure is common with hide glue used to make the piece originally.  Unfortunately modern glues have been used to do some repairs and these can cause problems and should never be used in furniture repair, always use hide glue for this work.  Hot hide glue is the best to use, but can be difficult and liquid hide glue is readily available and much better to use than modern glues.  See Using Hide Glue & Using Liquid Hide Glue.  The joint should be cleaned of dust and debris and any old loose hide glue should be removed but any that is still holding on the wood can be left on the joints.  It will be reconstituted when fresh glue is added to the joint.  I always wet down the old glue with hot water before gluing to help start the softening process.  Many old glue joints are prepared with a toothing or keying plane to score the surface before gluing.  If this has not been done, it is a good idea to do so to increase the surface area and enhance the glues holding ability.

Dry fit the joints back together to make sure everything is ready for the glue-up.  Certain joints need to be redone to make the work fit properly, some tongue and groove joints will open up on the top surface and don’t go back together until the back shoulder is planed down to make the face shoulder tight.  Shrinkage may cause the tongue to be too long and it can be shaved down a bit to fit properly.  Check to make sure that dowels properly fit into the holes, are not too long or too short.  To clean out dowel holes use a proper sized drill bit and run it into the hole by hand.  If you use a tool, especially a power drill, it might drill out wood and make the hole useless.  By advancing the drill bit by hand you are assured that the bit will only remove the glue and not the wood.

Double Dovetail Key

One traditional method for repairing a loose joint or split in the wood is using a butterfly key, double dovetail key or sometimes a Dutchman.  Some of these repairs are done all the way through the board to provide strength across the joint.  These do a good job of holding the wood together and are decorative if they show.  Most of these keys are inlet on the underside or the unexposed side and does not go all the way through the board.  The joint or split is cleaned, glued and clamped together.  After the glue has dried and while the piece is still in the clamps, the key is laid out across the joint.  The space is excavated and a straight-grained strong piece of wood is used to make the key that is fit into the space.  It might be easier to make the key and use it to layout the excavation or mortise for the key to fit into.  The key can be cut with the sides at a slight angle, this caused the joint or split to tighten as the key is driven in place.  The key is of course glued with hide glue to hold it in position.  After the glue is dry, the key can be planed and smoothed flat to the surface.

Matching grain with plug repairs

Dowels and pegs were used to reinforce joints and attach parts.  Sometimes it is necessary to replace broken dowels, which can be difficult to remove.  The method I use is to drill a small hole down the center of the broken off dowel or peg.  If it is 3/8” diameter dowel I will use a ¼” drill to make the hole.  I will flatten off the end of the broken dowel and with a scratch awl mark the center of the dowel.  I then carefully drill the smaller hole directly down the center of the dowel.  You can tell when you get to the end, as the drill will catch in the glue and give you a tactile warning when you have drilled deep enough.  I then use a narrow chisel to break out the remaining pieces of dowel.  Soaking the joint with alcohol to crystallize the hide glue can loosen stubborn dowels.  If you try and drill the 3/8” dowel out with a 3/8” drill there is a chance of drilling into the wood surrounding the old dowel.  This technique also works for square pegs.  Once you have the damaged dowel removed you can use a drill bit of the same size as the hole and advance the bit into the hole by hand.  If you use a brace you have an opportunity to accidentally drill into the wood, so just advance the bit by hand.  This will remove any remaining chips of wood and glue so the new dowel can be properly fit into the original hole.  The hole needs to be free of old wood from the dowel and most of the glue, but some glue can remain as it will be reconstituted when hot hide glue is introduced.  I always brush hot water into the holes prior to gluing to pre-soften the old glue and prepare the hole for the new glue and dowel.  The dowels need to be prepared before gluing in place, see Making and Using Dowel Pins and Pegs.

Repairing broken dowels & Dutchman edge repair

Another classic repair is the dovetailed Dutchman, done to the edge or side of the board.  This is a solid repair for areas such as damaged hinges or lock mortices.  Missing wood from wear, abuse or gnawing animal damage can be readily replaced using this traditional repair.  Mark out the damaged area by using a marking gauge to give parallel marks on the top and side of the board at the damaged area.  Remove as little of the original wood as possible, just the damaged area.  I then place a mark on the very edge at both ends of the damage.  I then nick the mark and begin sawing at a slight angle.  You can set up a bevel square if you need to, but I just eyeball the angle on both sides.  Make the kerf from one mark to the other.  Using a sharp flat chisel I remove the wood between the two marks left by the marking gauge and between the saw kerfs.  I also put a slight angle on each cut so that one side is wider than the other.  This taper makes for a better fit when the new piece is added.  I use a rasp to roughen up the wood prior to adding the Dutchman.  Select matching wood for both color and grain.  The grain match is more important than the color and the color should ere on the light side, as it is easier to darken than it is to lighten woods.  The Dutchman needs to be thick enough to fill in the space and the angles cut at each end corresponding to the angles cut in the old wood.  The Dutchman is also tapered and is wider on one side than it is on the other, when fit into place it will wedge tight as the glue dries.  Key or tooth the underside of the Dutchman to improve the glue holding ability.  After the glue has dried the wood can be smoothed down the original surface.  The new wood will need to be stained to match the original, see Staining and Chemical Staining.  This repair can also be done on the end of a board with just one angle cut on the inside.  The piece is prepared in the same way but it will need to be clamped, as it will not hold itself in place.

It is tempting to repair holes by gluing in a whittled piece of wood, but the grain is in the wrong direction.  When repairing holes it is sometimes advisable to use a drill and make the hole a uniform size and depth to make the repair easier.  Many drill bits will not drill into a hole very well, so whittle a stick and put it in the hole to give the drill somewhere to center.  A bit with a spur will make a better entry hole and a better repair.  By drilling a hole of a certain size, you can make a matching plug using a plug cutter of the proper size.  A set of plug cutters in different sizes allows you to make plugs with side grain and not end grain.  Orient the grain in the plugs to match the surrounding grain of the wood and glue into place.  After the glue has dried the plug can be smoothed down to the surface and stained to match.

Larger repairs of missing wood (lacuna) can be replaced by making inlays with matching grain.  Start with a thin piece of matching wood and locate it over the hole and move it around until the grain orientation and match is best.  Then cut the patch large enough to cover the hole and slightly bevel the edges to make a tight fit.  Certain shapes like diamonds and squares oriented diagonally are more invisible that patches with edges perpendicular to the grain.  If the grain in the patch and wood are at angles to the edges of the patch it will be less conspicuous.  Place the patch over the hole and with a sharp knife carefully cut into the wood around the edge.  Then use a chisel and or router plane to remove the wood inside the score lines to a uniform depth.  The depth should be enough for a strong repair but does not need to be too deep.  It of course should be less than the thickness of the patch.  Key or tooth the bottom of the patch, apply glue to both surfaces and drive the patch into place.  There needs to be a way for the air to escape on these tight patches and too much glue can cause a hydraulic problem when driving the patch home.  The beveled sides will make the joint very tight and hold the patch in place as the glue dries.  Smooth patch to the surrounding surface then stain and finish to match.  Patches to the edges or ends of boards should have angled cuts with proper grain orientation to make them less visible.  Use details such as the edges of beads, fillets and moldings to make the transition to new wood.  When gluing in some of these patches require some creative clamping to secure them while the glue dries.  See Clamps and Clamping.

When placing new wood into old wood one thing that is immediately noticeable is the difference in the texture of the old wood to the new wood.  You can chisel, plane, scrape or sand it smooth but there is a subtle visual difference.  I use a piece of wood that is just harder than the new wood of the repair to burnish the wood to make it look like old wood.  I rub the wooden burnisher with the grain of the wood and burnish only the new wood until it has the same texture as the surrounding wood.  This is best viewed at an angle to the grain to see the results.  If you do not do this there will be an optical difference between the old and new wood that shows up in the final finish.

Repairs to moldings can be done using many of the above techniques up to the point when you have to shape the new wood to match the details and curves of the surrounding moldings.  Small patches can be chiseled to shape then sanded and burnished to finish.  With the proper grain orientation the patch can be scraped to shape.  Larger lengths of repairs might require the use of a scratch stock with a cutter ground to match the existing molding.  It is then used to make the new wood repair down to the original surface of the surrounding molding detail.  See Scratch Stock article for how to make and use this handy tool.

Turned legs and spindles from chairs or tables are frequently broken and need to be repaired.  If the chair is going to be disassembled then the repairs can be done at that point.  Some spindles need to be repaired in place and will require some technique for doing the work in situ.  While the fractures can occur anywhere along the spindle it usually breaks on a narrow or thin detail.  Remove both pieces of the spindle carefully to keep the fracture fresh and crisp.  The break needs to be reinforced with a hardwood dowel of the appropriate size and it is sometimes difficult to drill down the center of the broken rough end grain of the wood.  A method of doing this repair is to make a very fine cut straight across the spindle at a detail where it will be hidden and close to the fracture.  Then take the short piece and glue and clamp it back into place carefully matching the fracture back to its original location.  After it has dried you can easily drill straight and matching holes in each piece.  A set of dowel pins will assist in marking the holes in the correct place.  This is a good method for repairing spindles when you can take the chair apart as well.  You have to get a dowel into the holes at the same time getting the ends of the spindles back in their sockets, so the dowel cannot be very long.  One method of getting around this problem is by drilling one hole deep enough for the entire dowel to go into the hole.  The dowel needs to be able to move freely in both holes.  A small hole is drilled at the bottom of the deep hole.  The ends of the spindles are placed in their sockets and the dowel joint lined up.  Then glue is injected into the small hole forcing the dowel up the hole into place.  Make sure all surfaces have glue on them prior to doing this operation.  As an alternative a small slot can be cut on the underside of the spindle into the dowel hole.  Then when the spindle is in place, the dowel can be manipulated into place and the slot filled with matching wood.  This technique allows you to make repairs to spindles and it can be used for loose square tenons to be able to assemble the joint without taking a piece of furniture apart.  While this technique is a bit tricky it can be a worthwhile method when making repairs to furniture that does not need to be disassembled.  Sometimes extra damage can be done to a piece when it is being disassembled and undergoing restoration work.  While this is unfortunate, it does happen and you should be ready for additional work that cannot be billed.  This is why it is important to repair the work in place if possible.

If you have to disassemble a piece with several identical parts such as stretchers or rungs from a chair you will need to label the parts so they go back in their original location.  By labeling or numbering the parts you will be sure to get them back where they belong.  If you use masking tape make sure it is the type for painters that won’t remove the original finish.

Do just the amount of repair necessary to bring the piece back to a usable condition.  Do as little as possible and leave as much of the original as possible.  The piece should be stabilized to prevent further damage, by not doing necessary repairs the piece can become more damaged.  And remember always use hide glue when repairing furniture and antiques.  On old pieces it is a good idea to document your work so future generations of conservators and restorationists will have some history of the piece.  A written document should describing the condition of the piece prior to restoration, what woods it is constructed from and any previous repair work should be noted.  The documentation should include what was done to the piece and what if any new materials were used.  Photographic documentation will also help in chronicling the history of the piece.  This can be invaluable to curators and collectors in the future by adding to the provenance of the piece.

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