Lacquer Retarder with Shellac
The right additives can help keep spray-applied shellac from drying in the air before it hits the workpiece. June 30, 2007
Question
I'm trying to dust on a toner coat using shellac (Bins), and I keep ending up with dusty nibs. Mottle, maybe. I think it's dry before it hits the surface. In a book by Jeff Jewitt, he recommends using a lacquer retarder in shellac when spraying. Has anyone tried this? Maybe this is the secret "Shellac Wet" product in disguise.
Forum Responses
(Finishing Forum)
From contributor U:
Try it on a scrap piece of wood. Make a sample. Can you spare the shellac and retarder for the experiment? Let us know what happens.
From contributor T:
Dry spray. A lacquer retarder like butyl cellosolve should solve the problem.
From contributor B:
Where do I get butyl cellosolve?
Here's another one for you. Shellac sticks to anything and anything sticks to shellac. And please, if anyone thinks the above is not true because of an experience they have had, please post it so I won't spray shellac over or under something I shouldn't.
From contributor Y:
It seems to me saying you can cover anything with shellac and put anything over shellac is too broad of a generalization. Yes, generally you can put shellac over most anything, but just recently a refinisher friend of mine related that he was repairing what he thought was a shellac finish, and the new coat of shellac he was applying would not dry. He ended up stripping the piece and then successfully applied shellac, having decided that there was some unknown contaminant on the old surface.
On the other end of this, putting other finishes on top of shellac usually works if the shellac is de-waxed. What I'm getting at is: if I'm not sure, I experiment on a piece of scrap.
From the original questioner:
I guess that's why I'm using shellac. I am new to shellac but I like everything about it except its rapid drying and unfortunately, you have to put something else over it for a proper finish.
From contributor M:
Do a Knowledge Base search for "shellac retarder" and get more confused! The problem with Homestead's shellac wet is that you are not supposed to topcoat it. I don't know which brand of shellac you're using, but Home Depot sells a de-waxed shellac called Pro Finisher - Universal Sealer. It's made by Zinnser and it's the same product as Seal Coat in a different package - I used it recently and it sprayed fine, even with a turbine HVLP. Adding more denatured alcohol or something more pure like Behkol (Mohawk) will help. Still waiting for a chemist to chime in and give something definitive!
From contributor Y:
You can use shellac as a top coat. All finishes have their pros and cons. It all depends on what you are using it on and what you expect from the finish. Shellac is more durable than it is sometimes given credit for.
From contributor S:
Shellac certainly has its place in finishing and restorations. You should get to know the limitations of shellac. There are other coatings that are more durable and chemical resistant than shellac, but they have their limitations, too. As an example: The more durable and chemical resistant the coatings are, the more difficult they are to repair. This is something to think about.
From contributor J:
Shellac wet is not a retarder. It is a siloxane additive (very similar to the wetting agents used in waterborne finishes) that acts as a surface tension reducer to avoid fat edge when using shellac. Over-coating shellac that has shellac wet added to it should not pose problems with any solvent based finishes, but some waterbornes may exhibit fisheye. Usually sanding takes care of the problem, so if you are using it, make sure the shellac is sanded with 400 before topcoating.
Generally you can use lacquer retarder for shellac. Butyl cellosolve (ethylene glycol monobutyl ether) is a standard retarder for lacquer but there are many different products or blends of products that are also used in making lacquer retarder that will work fine with shellac.
Turpentine will work in a pinch. The reason it was recommended in 'Great Wood Finishes' was because it's easy to get. If you have access to some of the more exotic solvents, sec-butanol works very well. It has a much less disagreeable odor than the other isomeric form of it called n-butanol. That's what I use for shellac at about a 10-15% ratio. Sec-butanol isn't easy to get your hands on, though.
All that said, shellac is not one of the easiest finishes to spray. Keep the coats light and you might be able to get away with adding nothing to it. What shellac wet does is keep the finish from rolling up on sharp edges (called fat edge or window-paning).
From the original questioner:
Thanks. Great book, by the way.
The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).
Comment from contributor R:
After many years and many finishes, shellac with carnuba wax top coats is in my view the finish for exotic woods. I use a Krenov method by diluting store bought de-waxed shellac three to one, then let the material settle for a day or two, decant the liquor and use this.
I use an Ox Ear Hair brush and brush out and let dry several coatings, then sand with 220 grit, reapply and sand again till the pores are sealed. If you like the pores to be revealed use fewer coatings. Finally rub with 0000 steel wool and wax. You will achieve a translucent warm finish which will reveal all of the curl, blister, birds-eye and other figure without any muddiness nor the plastic look of lacquers or urethanes.
Also the fragrance within a cabinet is delightful as one opens the door. Shellac is a very durable finish with the exception of alcohol or standing water contaminates.
