Sunday, September 21, 2014 Register
 
www.cyberspacesolutionsinc.com
www.cyberspacesolutionsinc.com Bookmark and Share
Search
 
 
Shellac Repair
 
Shellac Repair
Created by Steve on 8/29/2010 7:47:59 PM

Instructions on how to repair your damaged shellac finish


Shellac Repair

Leaf Divider

A great many antiques dating form the 19th century and before were finished with shellac.  Shellac was also regularly used by cabinetmakers working in the Mission, Arts & Crafts, and Prairie style. In fact, shellac finishes were quite common into the first half of the 20th century on all sorts of furniture items, including those made and passed down from family members.  Therefore, it is not unusual to encounter a piece of furniture finished with shellac that is in need of “refinishing”.  But, don't grab the stripper and sandpaper just yet. Shellac, unlike other finishes, is very easy to repair. Being able to repair the original finish means no chemical stripping and no patina destroying sanding. The ease with which shellac can be repaired means that the finish used by the cabinetmaker can often be preserved and returned to its original condition. And best of all, repairing the original finish is usually much easier (to say nothing of less messy) than stripping and refinishing.

Perhaps the most often mentioned disadvantage of shellac is that it is easily damaged by alcohol.  Ignoring for now that this "downside" is greatly overstated since most of the alcohol with which shellac finishes come in contact is in the form of alcoholic beverages.  And, since the alcohol contents in these drinks is quite low compared to the "pure" alcohol in which we dissolve shellac, actually "damage" from alcohol is rare. To illustrate this reality I offer two examples. 

First, if you have ever mixed your own shellac from dry flakes you know how long it takes denatured alcohol to dissolve the flakes of shellac.  Mixing shellac requires far more time than dissolving sugar in hot coffee. Clearly, if it takes hours for shellac to dissolve in 200-proof grain alcohol, how much longer will it take a beverage with far less alcohol to damage a shellac finish if someone accidentally spills an adult beverage in which the alcohol has been "thinned" to only 20 to 50 proof?

Second, at the beginning of my classes on shellac I initiate a demonstration of the durability of shellac by preparing a "mixed drink".  I have a small bottle in which I keep denatured alcohol cut 50/50 with distilled water to simulate a typical 100-proof "adult beverage" (denatured alcohol is almost 200-proof, or pure alcohol--not many among us drink anything that strong!).  I pour a shot of my "home brew" into a glass and add water to simulate a typical mixed drink.  I then "spill" my drink on a tabletop finished with shellac. Then, I proceed with my program.  Near the end, I return to the tabletop and remind those in attendance of my spill.  I simply wipe up the liquid that remains and ask those in attendance to examine the finish for "damage".  Fully expecting confirmation of all that they have been told, they inspect the finish only to find that there is no damage.  In point of fact, most of the alcohol has simply evaporated before it was able to do any damage to the finish.  "Myths" are very powerful in shaping "facts"!.  

Please understand; I am not suggesting that alcohol will not damage shellac. Clearly, long-term exposure to alcohol, even at low concentrations if it is trapped against the shellac film and not able to evaporate, will soften and damage a shellac finish.  My point, however, is that the mere mention of the word "alcohol" will not destroy all of your hard work. Shellac is not nearly as easily damaged by alcohol as some would have us believe. Therefore, your present shellac finish may be well worth restoring instead of stripping and replacing with a "modern" finish. 

So, even though shellac is far more durable than some would have us believe, we can take advantage of the "evaporative nature" of shellac to repair damage when it does occur. Since we know that shellac is dissolved in alcohol it stands to reason that we can also use alcohol to soften a dry shellac film. It follows, then that we can take advantage of this knowledge to repair a damaged shellac finish rather than resorting to stripping and sanding. Alcohol, properly employed, will allow us to return to the later stages of the shellac padding process to repair and/or restore a damaged or aged shellac finish.  Further, there is often no need to add more shellac; the shellac that is already there is sufficient to produce a “new” finish.

Testing the Existing Finish

Before begriming to repair an existing shellac finish is it a good idea to test the finish to be sure that it is indeed shellac. "What is that Finish?" is a short article describing a simple test you can use. Please note that old nitrocellulose lacquer can be removed with denatured alcohol. Therefore, in performing these tests be sure not to rub the surface. Just apply the solvents and let them to the work.

Restore the Original Finish

Even if the present shellac finish is damaged, heavily “alligatored”, or contains bare spots from which the original finish has been worn thin (or even removed) the finish can almost certainly be restored.  It is also quite possible that the restoration can be undertaken without adding “new” shellac.  If shellac must be added we will need to make every effort to duplicate the original grade.  The process we will follow will begin with the later stages of the padding technique.  It is very probable that this is the same application technique used by the original finisher.  If you have not padded shellac you may want to read the padding information (see Applying Shellac) and practice this technique to some test panels before you proceed. 

Make a new pad for this process (see instructions in Making a Shellac Pad).  Our initial objective is to soften the existing shellac so that it can be easily spread into the restored film.  To do this we will use only alcohol in our pad.  Unlike some of my earlier padding instructions, in addition to the alcohol in the pad we will also apply a “liberal” amount of alcohol to the surface so that it will begin to soften the shellac across the entire surface, not just the area that we are working.     At this stage we will not lubricate the face of the pad with mineral oil; the higher than normal amount of alcohol will provide sufficient lubrication. 

Begin by charging your pad with alcohol following the instructions in Applying Shellac.  Then, while the alcohol is still handy, squirt a stream of it on the surface.  Confine it to the area you will work initially; typically I work an area that I can easily span with my arm comfortably extended.  Next, land the pad (the technique is not critical here, but it provides an opportunity to practice) somewhere in the middle of the area to be worked and quickly spread the alcohol that you just squirted on into an even film over your work area.  Then, beginning at a point that is furthest from your off-hand (I am right-handed so I begin to my left at the point furthest from me) work the pad over the surface in a series of “Os” and figure eights while applying moderate pressure, until you reach the point opposite your starting point.  The key here is even coverage; whether you proceed up and down, or from left to right is not important.  Just make sure that you work all of the area.  Continue padding (still applying moderate pressure) by returning quickly to the starting point and begin the process over again.  As the alcohol evaporates from the surface apply more from your squeeze bottle so as to maintain its solvent action (Use caution and judgment.  The objective is to keep the surface wet but not “puddle”.) 

In short order the shellac will begin to soften as evidenced by the appearance of swirl marks left by your pad.  When these swirl marks are more or less uniform over the entire surface you are ready to begin to refine the renewed finish.  At this point you will no longer add alcohol directly to the surface being worked; all future alcohol will be added to the inside of the pad in accordance with the instructions in Applying Shellac.  You will also begin to use mineral oil to lubricate the face of the pad as you reconstitute and refine the shellac into a restored film. The instructions for the process are exactly the same as those for padding shellac so refer to that material as you continue to repair the shellac finish. 

One final note of caution is in order.  Unless someone has physically removed shellac from the piece you are restoring it is very unlikely that you will need to add any new shellac throughout this process.  This is particularly true if the shellac finish that you are restoring is badly “alligatored”—an indication of a shellac film that was applied too heavily (even the old-time finishers got it wrong from time to time).  However, if there are areas where there is significant loss of shellac from sanding, stripping, or abrasive action in use, you may need to add small quantities of shellac to your pad.  If this is necessary follow the instructions in Applying Shellac having to do with “bodying” or applying the base at the beginning of Step Two of those instructions.  You will also need to match the grade in so far as possible.  Typically, if the shellac is dark this will mean using either garnet or seedlac.  If the shellac finish is lighter you will likely use blond or orange.  DO NOT use pre-mixed shellac.  It does not pad well, and once mixed with the existing finish may lead to total removal and starting again. 

Removing a Shellac Finish

On occasion you may need to remove a badly damage shellac finish because it is simply too worn to repair, or because the surface of the underlying furniture needs to be repaired.  Removal may also be indicated if you want to refinish with a different finish.  Please use caution in coming to this conclusion.  Much of the value of true antique furniture is in its original finish (I am speaking here about furniture that legitimately qualifies as "antique", not just old furniture that is in bad need of refinishing). 

In removing a shellac finish we will again rely on the ability of shellac to be dissolved by its solvent, alcohol.  Therefore, begin the process by applying a liberal amount of  alcohol  to the surface from which the shellac is to be removed.  I generally dispense alcohol from a squeeze bottle and spread it around with a pad or inexpensive brush.  My objective is to wet the surface with alcohol and keep it wet for a period of 10 or 15-minutes before I begin to remove the shellac.  Clearly, on vertical surfaces I have no choice other than to keep padding alcohol on before it dries, thus keeping the shellac "bathed" in alcohol.

I then use one of two methods to remove the old shellac finish.  Perhaps it would be more precise to say that I typically begin with one method and end with the other.  I begin removal of the old finish with a card type cabinet scraper on which I have rolled only a small bur; my objective is only to remove the finish, not the wood.  This is a easy edge to produce.  Simply joint or flatten the edge of the scraper and then apply a small "hook" with just light to moderate pressure with the burnisher.

I move the scraper with the grain while applying moderate downward pressure to the shellac finish.  Great gobs of alcohol softened shellac will be removed with every pass, resulting quickly in the almost total removal of the old finish.

I then squirt more alcohol on the surface, spread it around, wait a few more minutes and then vigorously attack the remaining shellac film with a "removal" pad.  This pad is constructed in exactly the same way as the pad described in Applying Shellac with one significant exception—the outer covering is burlap.  By burlap, I am not referring to the civilized, soft stuff sold in many colors by your friendly neighborhood fabric store, and used to make coverings for bulletin boards (some stores also carry the "real" stuff).  This is the industrial strength stuff, the Biblical garment of contrition known as "sack cloth".  It has the abrasive qualities of 80g sandpaper to dislodge the softened shellac.  It also has large spaces in the weave of the fabric to gather and hold the shellac once it is removed.  Periodically, the shellac trapped in the material must be flushed out with a quick rinse and wring in alcohol.  In use, this pad is to be literally scrubbed over the surface to remove as much of the remaining shellac as possible.  The burlap cloth alone, without the wool reservoir, can be opened and "sawed" back and forth over turnings, edges, and other difficult to reach places.  It can also be wrapped over the end of sticks of various shapes and worked into groves and carved detail to remove shellac from these difficult to reach locations.

Why Burlap and not Steel wool?

Very simple.  Does the term "rust" come to mind?  Steel wool quickly disintegrates leaving tiny shards of steel (a ferrous metal) behind.  Ferrous metal rusts!  "Oh, but I wiped the surface to get rid of all the steel wool."  Sure you did!  Just like the wipe down with mineral spirits got rid of all the silicone furniture polish residue on your last refinishing job, which is why you are still trying to figure out why you still got all those little craters in our finish.  You may get most of the shards—you will not get them all (we'll solve that problem in another article).

"Well, yes; but, I am not using a water-borne finish ...I know that would create a rust problem, so I would never do that."  Nice try, but the problem is than NO finish is water-proof.  Understand that the issue is not liquid water; the problem is water vapor—a.k.a. relative humidity.  No finish is impervious to the passage of water vapor through the finish with seasonal changes in humidity that cause moisture to move in and out of the wood.  Some finishes are far more porous than others.  Oil and wax finishes, for example, offer virtually no protection at all.  Lacquer is only marginally better.  Even the most moisture  resistant finishes, gloss varnish (including polyurethane) and shellac, are not impervious.  In time even these finishes will allow the passage of water vapor thru the finish film.  As that occurs, steel wool shards left behind, firmly embedded in the finish,  are going to rust.  Your finish is going to develop a "freckled" completion.  In my never to be humble opinion, steel wool has absolutely no place in the finish room, with the possible solitary exception of rubbing out a completely cured finish. 

After the Scraper and Burlap Pad

Having successfully removed the old shellac finish you can now undertake necessary repairs and begin to apply the new finish.  You will not have removed all of the shellac, but this is not a problem.  Shellac is frequently used as a "sealer", so you can view the shellac that remains as the sealer coat for your new finish.  Its presence, by the way, will go a long way to preserving the patina that has developed in the wood over time.

If you are going to reapply a shellac finish refer to the article on Applying Shellac.  You may also want to apply a shellac "color coat" and then topcoat with varnish or lacquer.  You can also apply a water-borne finish if you are so inclined.  The point is that you have successfully removed the old shellac finish without the use of a harsh chemical stripper or aggressive sanding.  Your antique is much the better for the experience.

Leaf Divider

powered by metaPost
print
rating
  Comments

  
 
 
www.cyberspacesolutionsinc.com
 
 
www.cyberspacesolutionsinc.com www.cyberspacesolutionsinc.com www.cyberspacesolutionsinc.com