Sunday, July 23, 2017
 
www.cyberspacesolutionsinc.com
www.cyberspacesolutionsinc.com Bookmark and Share
Search
 
 
Applying Shellac
 
Applying Shellac
Created by Steve on 8/29/2010 7:46:59 PM

How to apply shellac; tips, tricks, and lessons learned...




Applying Shellac

Shellac is very easy to apply as long as you keep its properties in mind and avoid the temptation to apply it the same way you would varnish, lacquer, or a water-borne finish.  Shellac is an evaporative finish; it dries by solvent evaporation. There is no curing involved. Since the solvent is denatured alcohol, the evaporation rate is quite rapid.  If you attempt to apply shellac in the same way (or using the same techniques) that you would an oil-based varnish or a water-borne finish you will be very disappointed with your results.  If you apply multiple coats as you would when applying lacquer, the finish film will become too thick and will quite likely "alligator" (develop cracks and separate into "plates" similar to an alligator skin). Shellac can be brushed, padded, or sprayed; all with good results. When applied to small components, it can even be dipped.  But regardless of the application method chosen, it is important to avoid applying too much. This tendency can be a major problem when spraying.

In this article I will focus primarily on brushing and padding since I believe that these methods produces the best results in the majority of fine furniture finishing applications. Spraying comes in a close third only if the finisher wielding the gun understands the importance of keeping the finish film thin. Between padding and brushing, I prefer padding when applying a shellac only finish. Brushing works well when the shellac is being applied as a "sealer" beneath some other finish. For example, I often brush on a single coat of shellac before I varnish. A sealer coat of shellac is also an excellent way to "warm up" a water-borne finish. I also use shellac as a "barrier coat" when working with naturally oily woods, or when applying a new coat of finish following stripping of a previous finish. As a barrier coat, shellac prevents oils and contaminants such as silicone from creating adhesion problems with the new finish.

There are two basic ways to use shellac in a finishing schedule—shellac can be the sole finish; or, shellac can be used as a "sealer coat" beneath a topcoat of varnish, water-borne finish, or lacquer (lacquer over shellac presents some potential problems that will be discussed below).  When used under another finish, shellac provides a number of benefits to the finish. As already mentioned, shellac is an excellent "universal sealer". But, it may also be used to impart color and depth to the finish. Shellac can also serve as a "grain filler", or simply as an added barrier to moisture in high humidity environments such as kitchens and bathrooms. (For an examination of these properties see Shellac, The Miracle Finish Of The 21st Century.)   

Brushing Shellac

Brushing is the easiest way to apply shellac in terms of the simplicity of the tools with which it is be applied.  When brush, I prefer a 2-pound (2#) cut.  When brushing shellac as a sealer coat under a topcoat I am far less demanding with respect to brush selection, and a bit more "free-form" with respect to technique.  I use an inexpensive natural bristle brush of the sort that can be found in the bin near the paint counter in the big box stores. Hardwood Lumber & More... sells a brush called "The Fooler" that looks similar to these disposable brushes, but has about twice the bristle content that makes an ideal shellac brush.  I load the brush by dipping about 2/3 of the bristles into the shellac.  I then apply the material in long strokes, brushing with the grain allowing the shellac to "flow" onto the surface from the tip of the brush.  I work rapidly from the "wet edge" but with almost no overlap of the previous stroke.  Recall that shellac dries by evaporation.  Since the solvent is alcohol, and alcohol evaporates very quickly, shellac begins to dry on contact.  Any brush overlap will raise a rough surface and may leave a "brush mark" that you will have to remove.  In the same way I keep "over brushing" (going back over areas to which I have already applied shellac) to a minimum.  Any technique in which you brush over an area already covered with shellac is going to raise a rough surface and again, very probably leave brush marks.

If you have a large area to finish you may want to retard the drying rate of the shellac so as to keep a wet edge longer. This is easily done by adding one tablespoon of pure gum turpentine to every eight ounces of liquid shellac. Even so, over brushing should be kept to a minimum.

(NOTE:  I said gum turpentine, not paint thinner/mineral spirits.  Turpentine, like shellac, is a natural resin.  Further, like alcohol, it is refined from a plant not petroleum.  Therefore, turpentine is a compatible solvent; though it should not be used as the primary solvent.)

When the shellac is dry lightly sand with 320P open-coat aluminum oxide sand paper. On flat surfaces, sand with a backer block. After sanding, wipe the surface clean with mineral spirits to remove sanding debris before you apply your topcoat.

Padding Shellac

Applying shellac by padding is an age old process that is easily mastered with just a bit of practice. Using this technique one can quickly obtain a beautiful, high gloss finish with incredible clarity that will bring out the depth and character of wood as no other finish can, with the possible exception of "French polish".

This raises an important point. "Padding" and "French polishing" are not the same thing. Padding is used in applying a French polish; but, there is far more to the French polish technique than there is to padding. French polish will be covered in a separate article.

Padding is a three step (loosely defined) process in which a thin (very thin) shellac film is applied and refined to produce an optically clear finish that will literally last for centuries. The process is as follows:

  • First, the shellac "body" is applied using a simple tool which is variously identified as a pad, fad, rubber, or tampon. The objective of this step is to apply a uniformly thin film of shellac that will be refined in later steps to produce the desired finish. Little effort is made to do anything but lay down the shellac foundation, or body in this step.
  • In the second step the shellac body is refined and leveled. Deviations in film thickness and gaps in coverage are corrected and the excess lubricant and "swirl" marks left over from the bodying step are removed.
  • In the final step the shellac is polished to a high lusted. Any remaining blemishes are removed and all remaining swirl marks left from the previous steps will be eliminated.

Step One (Bodying)

Begin Applying the shellac by "landing" the pad on the surface in the same way an airplane would touch down on a runway.  Then glide the pad across the surface in a pattern of overlapping "Os", and figure eights, making sure to evenly cover the entire surface.  Transfer shellac to the surface by applying more and more downward pressure on the pad until increasing the pressure no longer forces more material out of the pad and the pad begin to stick or drag. 

Begin with large figures when the pad is freshly filled and reduce the size slightly as you increase the pressure.  When you feel the pad begriming to drag or stick, following the airplane model, "take off" again.  Don't stop your padding motion and abruptly lift the pad from the surface. That will cause a blemish. 

Open the pad and apply additional shellac as described in the instructions on making and using a pad. Then close the pad and add another drop of mineral oil to keep the pad lubricated, "land" the pad on the surface, and continue the padding process until you have applied an even film of shellac to your project.  The French polishers of the past referred to this processing as "bodying" the finish; the laying down of a more or less uniform layer of shellac that would be work into a smooth finish in subsequent steps. We will retain the term here.

Your visual "key" for having reached the stopping point for the bodying phase is the building of a more or less even film of shellac.  The "color" will appear uniform from the corners and edges through the center of the panel.  Don't be alarmed if there is a bit more "build-up" at the edges.  This is to be expected until your technique improves.  Also, don't be concerned that the surface is a bit "rough" in comparison to your mental image of how a shellac finish should appear.  You will notice pronounced "swirls" and "clouds" of oil on the surface of the shellac.  This is not a cause for concern, but is a by product of the oil you used to lubricate the pad.  These "defects" will be removed in coming steps.  Understand that this is not your "finish".  This is only the somewhat ugly foundation; the beginning of the finish to come.  None of these apparent "glitches" should lead to disappointment with your decision to attempt padding shellac.  As you consider them just remember that I told you that at the conclusion of the bodying step your finish would not look particularly good.  More to the point, it will probably look pretty bad.  No matter, stop at this point and allow the shellac to dry.  Continuing to work this surface by apply more shellac will not improve the look.  In fact, it will only make things worse and lead to real problems.  If you apply too much shellac the problems will become very real.  Allow the shellac to dry for at least 30-minutes to an hour.  You can quit until the next day (or several days) if you like.  When you are ready you will simply pick up with Step Two, the refining step. problems.  The imperfections that you see now are only

Step Two (Refining)

In the first phase we applied our shellac body.  You are now ready to refine your finish.  From this point on we will concentrate on leveling and smoothing the finish, and raising a lustrous shine.  As we begin this phase, keep one very important thought in mind.  Too much shellac creates a bigger problem than too little.  It is always easy to add shellac where needed.  It is much more difficult to remove excess shellac when you have applied too much.  Therefore, avoid the natural temptation to keep building up a finish film as you would with varnish or lacquer.  The objective with shellac is to spread a thin, even film.  It is not to build up a thick, multi-layer finish consisting of many "coats". In point of fact, you are working on the first and only coat of shellac you will apply. You are refining the shellac you laid down in the bodying phase.

As you begin this step or phase, your shellac finish should already have a modest sheen, albeit masked by swirls of oil and some "ridges" of shellac buildup.  Begin the second phase by examining the surface for evidence of areas where you do not yet have enough shellac.  Such areas will appear dull, and lighter in color when compared to the surrounding area.  They may also appear noticeably "thin" in comparison to the rest of the surface.  Also look for areas where you clearly have too much shellac.  These areas will have much more shine and be as "thick" as the other areas are dull and thin.  For most beginners, the areas with too much shellac will most likely be at the edges and corners of your work.  If you have no such problem areas congratulations; and, please be patient while I spend a few paragraphs with those who do. 

  • If you have dull areas (too little shellac) but no areas of buildup indicating too much shellac, proceed by filling your pad with a mixture of shellac and alcohol. Reduce the volume of shellac in your pad by one-half and replace it with an equal volume of alcohol.  The test for a properly loaded pad is the same as before.  Now, begin by concentrating on the dull areas.  These "thin" areas need a bit more bodying.  There is already some shellac there, just not quite enough.  Land your pad in the dull area and begin to work out toward the edge.  You will soon fill in the dull areas.  As you do, reduce the amount of shellac in your pad to just a few drops and then take a few passes over the entire surface as evenly as possible to blend everything together.  When you have finished allow the shellac time to dry before you again return to the beginning of Phase Two to check your work before continuing.
  • If you have a combination of dull areas combined with areas with too much shellac (too little shellac along with areas of too much shellac evidenced by dark shiny areas), or possibly just areas with obviously too much shellac (thick shiny areas, but no dull spots), then begin by loading the pad with alcohol only.  After applying a drop of oil to the face of the pad, land the pad in an area with too much shellac and, working more slowly than before, soften and spread the shellac build-up into the adjacent area where the shellac is thin.  Using alcohol only and moving the pad more slowly will soften the shellac.  As the shellac softens, you will be able to spread it into the dull areas by increasing the size of your work area.  Each time you reload the pad, return to the area of heaviest buildup and work outward into the areas where there is not enough shellac.  You are literally dissolving shellac in the areas of heavy buildup and spreading it into the areas where you laid down insufficient material.

As the surface appears more even, begin to move the pad over a wider area.  Finish by going over the entire surface as evenly as possible to blend everything together.  When you have finished allow the shellac time to dry before you again return to the beginning of Phase Two to check your work before continuing.

Now, on with Phase Two.  Begin (or continue) the second phase by filling your pad with alcohol only.  Again, close the pad and add a drop or two of oil.  Returning to the "airplane" model, land your pad on the project and continue as before.  This time, however, you are re-dissolving the finish already applied and spreading it into a thin, even film.  Keep that thought in mind to help focus your attention on keeping the pad moving evenly over the surface.  Don't concentrate on either the middle of your work surface or the edges.  Work evenly over the entire surface so as to produce an evenly distributed film of uniform thickness over the entire piece.

As you work you will soon notice a distinct difference—your finish is beginning to shine and is also becoming very smooth.  The "swirls" of oil and shellac that were so evident in the first phase will begin to disappear.  Don't over do it.  When the luster is more or less uniform and the surface is smooth, QUIT!  You will have removed all of the shellac "ridges" and much of the oil at this point.  The sheen will be even and the surface will be level, but you will still have some noticeable oil on the surface; not as much, but still visible.  Wait at least 30-minutes before continuing to the final phase—again, you can wait as long as you like.

Phase Three (Polishing) In the final phase, again to borrow a term from the French polishers, we will "spirit off" our finish.  For this phase you will need a new, clean pad.  Make it as before.  This time, however, you will use no shellac at all.  Open the pad and LIGHTLY fill the reservoir with alcohol—use ONLY alcohol.  The pad should also be much "drier" than before.  You will use no oil to lubricate the face of the pad.

Using the same technique you used to apply the shellac, only with a very light pressure, work the surface evenly to remove all of the remaining oil from the surface and polish the finish to its final luster.  The oil that is already on the surface should transfer to the pad thus "clearing" the finish and giving the pad the minimal lubrication necessary.  This is a difficult process to get right without lots of practice.  Too much alcohol and/or too much pressure will dull the finish.  Should that occur, resort to a miniscule bit of oil on the pad to "fix" the damage.  Use just enough to lubricate the pad, but no more.  Keep your pad constantly in motion and apply the lightest of pressure.  After one or two quick tours over the surface in the customary "Os", and "8s", switch to a series of parallel and slightly overlapping "touch-and-go" landings and take-offs.  You are just kissing the surface as you skip quickly to your take-off point.  This motion should be with the grain.  In brief minutes your finish will be complete.

Combining Brush and Pad

When applying a shellac only finish (no topcoat) I believe that the padding technique will produce the best results. With practice, you will find that the process goes quickly and, by its very nature, you are spared runs, sags, and annoying brush marks that have to be mechanically removed after the finish is applied. However, there are times when it is appropriate to apply shellac with both a brush and a pad. In these cases I brush with my right hand (I'm right handed) and wield the pad in my free left hand.  For example, on project that contain moldings, turnings, or carvings, brushing the shellac on to these areas and then refining the finish with a pad can be very effective. Brushing shellac into carving, turnings, and moldings makes it much easier to get shellac into the depths of the detail. I always finish these "detail" areas first and then blend them into the rest of the piece. Clearly, brushing and padding won't produce the same level of sheen in the recesses of these detail areas that padding will on flat surfaces; but, that's ok since the difference in sheen will add depth to your work.

As before, I dip about 2/3 of a natural bristle brush into the shellac and then "flow" the shellac into the the detail. A smaller brush is easier to use.  I begin at the top of the piece and work down. I also apply shellac to the detail areas before padding the flat surfaces. This eliminates the problem "drips" falling on the already finished surface. Such drips would be no problem with a slower drying finish (they could be easily brushed out), but they will create blemishes when using fast drying shellac that cannot be over brushed.

Another challenge when brushing shellac arises when "cutting in" the transitions between detailed areas and the field (the flat expanses) of your project.  Again, with a slower drying finish such as varnish this presents no particular problem.  You simple finish these areas first and then, working from the still wet edge, blend them into the rest of the finish.  But, when you attempt the same technique with shellac you will almost always be treated to a "blemish line" where the two finish areas meet. To eliminate this problem, combine the use of the pad with the brush. Brush shellac into the detail as described above and then run your pad (which is in your free hand) along the transition to "feather" the shellac edge into the unfinished field. (This same technique is used when applying shellac with a brush in case interiors. At inside corners, apply shellac to the corner first and then run your pad along the joint between adjacent faces to eliminate the brush "ridge" before applying shellac to the case sides, back, top, and floor.)

After I have brushed shellac onto all of the detail areas I return to padding to finish the flat areas. As I pad in the area of the moldings, carvings, and other detail I simply include them in my padding action. But, I am concerned only with the high or exposed areas of the detail. The areas easily reached by the pad develop the same sheen as the rest of the piece. Those areas that are below surface level (the nooks and crannies of the detail) are not hit by the pad, thus they remain a bit rougher in texture and exhibit less sheen. This alters the reflectivity of these areas making them appear darker and adding to the visual appeal of the detail.

When applying shellac to frame & panel construction I apply shellac to the boundary between the panel edges and the frame first. Depending on the profile of the panel and the frame I may use the same brush and pad combination that I used on mouldings and carvings above. I frequently apply shellac to the panel before assembly if the profile is simple and I want the high sheen of the padded finish to extend to the joint between frame and panel. When there is more detail milled into the transition between frame and panel I prefer the "shadow line" that I get with the different texture produced by the brush. 

Some Final Thoughts

Here is a general rule-of-thumb that has served me very well.  When padding shellac the first application should be all shellac.  In the second phase your pad should contain one part shellac and 1 part alcohol while fixing "glitches" left over from phase one.  You should then reduce the shellac volume as the defects are repaired.  In the final phase your pad should contain nothing but alcohol.

Your objective throughout the entire process should be to get even coverage with no build-up at the corners or edges.  In addition, the best finish is achieved with the thinnest shellac film.  Whenever I do shellac demonstrations I hold up a single large shellac flake and ask those in attendance to visualize dissolving this flake in alcohol and spreading it in an even film over the entire surface of the sample top being finished.

Finally, the solution to virtually all problems that may arise with your finish is alcohol.   Too much shellac in an area—reach for the alcohol pad and begin to spread the buildup into areas with too little shellac.  Too little shellac in an area—reach for the alcohol pad and begin to spread shellac from other areas into the area that is thin.  The surface is rough—use the alcohol pad to smooth it.

I hope that these instructions will be helpful.  In the end, the best way to learn these techniques is to get an armload of "test" boards and practice, practice, and then practice some more. Once you experience the depth, clarity, and radiance of a proper shellac finish I suspect you will reach for polyoneverythane far less frequently.


print
rating
  Comments

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