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View Full Version : The use of shellac in boat building



Jay Greer
04-04-2007, 08:30 PM
Hi Group,
Reciently, on another site, the use of shellac was questioned. So, I thought that a few words of Common Sense might be appropriate here.

Shellac has been used as a finish and sealant for over two thousand years!
It is benign so far as its considerations as being a toxic or polluting compound. Today it is still used in phamaceuticals as a pill coating and has a myrad of uses as a coating and sealant in furniature making. The finest finish in the world, the French Polish, is based on the use of shellac in a process that is very laborious .

So far as its use in boat building, I personaly always coat any wooden component that is to be bedded with a brush applied layer of thin shellac in order to seal the wood and prevent the leaching of oil based bedding coumpounds such as Dolfinite. Shellac will effectively prevent the intrusion of moisture into the inner surfaces of a hollow wooden mast. Herreshoff used it for bedding double planking on all of his boats. Planking set in thick wet shellac will remain tight but can be easily taken apart if necessary. It is so effective in this respect that the Egyptians used it for the same purpose some 2,000 years ago in ship construction as well as sealing mummy cases.

Shellac is cheap, easy to apply and dries almost instantly. The only drawback is that it has little resistance to weather and so should not be used where it will be directly exposed to the elements.j
Fair Winds,
Jay Greer

Fitz
04-04-2007, 08:39 PM
I've been using a couple of coats on the interior of canoes before varnish.

Old Town used to use it too, at least some during the war years according to the build records of canoes.

Nice sealer.

http://www.imagestation.com/picture/sraid204/p8170003f326dbe2bda3fa3b020670ffc/ef546c7b.jpg

tundra ted
04-05-2007, 12:41 AM
ive been using shellac for my interior work instead of varnish for some time.

Bob Cleek
04-05-2007, 01:57 AM
Orange shellac is also great for sealing fancywork. Several coats will produce a mahogany brown color. It is particularly good for ropework exposed to the elements, such as coachwhipped tiller handles and stantions. One interesting feature is that, although it will weather and crack, a regular thin coating of light cut shellac will restore the gloss and seal the cracks. Shellac is always soluable in alcohol.

outofthenorm
04-05-2007, 08:36 AM
Jay, do you have any more info or insight into how Herreshoff used shellac in double planking? Since it drys so fast, how did they get the shellac to stay wet while the plank was fastened?

Norm

Jay Greer
04-05-2007, 10:08 AM
Remember that Herreshoff jig built his one design hulls inverted. Which insured rapid construction. The planks pattern cut that were set by a full building crew. The shellac was much thicker than normal and so took longer to set. If the work was done during colder seasons, drying time took longer as well.
Jay

RodB
04-05-2007, 11:43 AM
JAY,

Is shellac a good choice for trim or ceiling beams in the interior of a boat where you don't want to varnish or have considered leaving the wood natural or at minimum sealed?

RodB

David G
04-05-2007, 01:38 PM
I've been a woodworker for 30+ years. Over that time, I've used shellac for a wide variety of tasks. One of my favorites, which hasn't been explicitly mentioned yet - as a sanding sealer. I've used it very successfully under a wide variety of finishes. I especially like it under water based lacquers. There, it provides some of the warmth and depth of finish that is still lacking - even in the best of the water based clear topcoats (the co-polymer process that cures the water based topcoats makes a warm, deep look impossible - for the time being). As a sanding sealer, beyond the beauty, shellac has these added advantages: dries quickly; doesn't stink up the joint; really stiffens the whiskers of wood that need to be knocked down; sands really quickly; doesn't clog sandpaper; leaves a very smooth surface -ready for the next coat. For many years, I mixed my own. Now, I mostly use the Zinsser brand. Their "Seal Coat" is approximately a 1.5-2 pound cut. I use it as a sealer. Their "Shellac" is about a 3 lb. cut IIRC. I use it as a topcoat.

Jay Greer
04-05-2007, 05:15 PM
JAY,

Is shellac a good choice for trim or ceiling beams in the interior of a boat where you don't want to varnish or have considered leaving the wood natural or at minimum sealed?

RodB
Shellac can be used as a sealer under interior varnish. Due to it's tendency to discolor when contacted by a damp object I would avoid using it as a final finish.
Jay

Rob Stokes, N. Vancouver
04-05-2007, 05:43 PM
I've been a woodworker for 30+ years. Over that time, I've used shellac for a wide variety of tasks. One of my favorites, which hasn't been explicitly mentioned yet - as a sanding sealer. I've used it very successfully under a wide variety of finishes. I especially like it under water based lacquers. There, it provides some of the warmth and depth of finish that is still lacking - even in the best of the water based clear topcoats (the co-polymer process that cures the water based topcoats makes a warm, deep look impossible - for the time being). As a sanding sealer, beyond the beauty, shellac has these added advantages: dries quickly; doesn't stink up the joint; really stiffens the whiskers of wood that need to be knocked down; sands really quickly; doesn't clog sandpaper; leaves a very smooth surface -ready for the next coat. For many years, I mixed my own. Now, I mostly use the Zinsser brand. Their "Seal Coat" is approximately a 1.5-2 pound cut. I use it as a sealer. Their "Shellac" is about a 3 lb. cut IIRC. I use it as a topcoat.

It should be noted that Zinnser's Seal Coat is dewaxed. this is (vitally) important if you plan on over-coating it with another finish and makes it an even better choice for undercoating.

Rob

Greg Nolan
04-05-2007, 06:13 PM
Shellac has been used for a long time on the bottom of wood and canvas canoes, instead of marine or other kinds of paint. It is more slippery than paints, does not scratch so readily, and is easily repaired and recoated, and so is a good finish for canoes that will be used in shallow rivers with sandy/rocky bottoms. Stelmok and Thurlow write about this practice in their book "The Wood and Canvas Canoe" and Thurlow (Northwoods Canoe Co.) regularly builds canoes with such a bottom finish. Only the bottom is coated, directly over the canvas filler, with orange shellac. The shellaced area is separated with a thin painted line at or just above the waterline from the upper part of the hull which is painted. I have used canoes finished in this manner; I find them attractive and have been told that they are reasonably durable, with minor dings and scratches readily fixed.

David G
04-06-2007, 11:16 AM
[QUOTE=Rob Stokes, N. Vancouver;1543455]It should be noted that Zinnser's Seal Coat is dewaxed. this is (vitally) important if you plan on over-coating it with another finish and makes it an even better choice for undercoating.

OK, this is the first time I've used the quote button. Hope I do it right. Yes, that is a key point, if you're gonna overcoat. If you're mixing your own, some suppliers offer a limited range of dewaxed flakes. Most flakes, however, retain their natural wax content. If you're planning on putting another finish over that shellac, it would be wise to read up on how to dewax your batches. It's not at all hard - but is necessary. To skip that step is to court disaster. In those limited applications where shellac is all you're putting on (I do this for some drawer boxes, for instance), the wax matters not.

George Roberts
04-06-2007, 12:29 PM
I though Shellac was a very poor sealer where water could make contact.

There are certainly better sealers for use around water.

Lew Barrett
04-06-2007, 12:55 PM
Shellac can be used as a sealer under interior varnish. Due to it's tendency to discolor when contacted by a damp object I would avoid using it as a final finish.
Jay

All of my boat's interior brightwork was sealed with shellac, probably at the yard in 1938. It was then overcoated with varnish. By the time I got her in 1994, the finishes had all broken down, were blistered and bubbled, and quite dark, some ranging to black. On the other hand, most of the wood still retained it's finish, and after almost 36 years
of service, what negative comments might be made?
It was however, difficult to remove, pretty much resisting fast work with a heat gun and requiring chemical stripping and sharp scrapers to get it down for refinishing. I suspect sealing with shellac was very common practice around here in pre-war years.
Lew

Jay Greer
04-06-2007, 01:51 PM
One of my sidelines is that of a fine woodwork art conservator. This brings me in contact with a lot of damaged finishes that are in need of special restoration techniques. Shellac finishes are the easiest to work with as they can be, easily, disolved with alcohol. The worst is what is known as, copal varnish, applied over shellac. It crazes and turns black, requiring maddening amounts of attention to set it right without destroying its antique value. Modern varnishes do not contain the resins and oils that were once used in making copal varnish and so do not have the adverse reactions when used over a shellac sealer coat.
Jay

Lew Barrett
04-06-2007, 03:54 PM
It crazes and turns black, requiring maddening amounts of attention to set it right without destroying its antique value. Modern varnishes do not contain the resins and oils that were once used in making copal varnish and so do not have the adverse reactions when used over a shellac sealer coat.
Jay

Very similar description to my experience. There was a goodly amount of bubbling and blisters, odd crazing patterns and very dark patching. My kids used to pop the blisters, that is until I pulled it all off and recoated with modern varnish. It was a gruesome job that ended in a satisfying result, but it's not something I'd like to do again.