Shellac

Larry Meyer

Wooden Canoes are in the Blood
I have a canoe with a shellac bottom and lately issues have cropped up that I think are due to having used Zinzer’s amber shellac that was not fresh enough. I understand that canned shellac has a shelf life of six months and I read that Zinzers has found a way “to extend the shelf life to 3 years, “ but I doubt that claim.

Every can of Zinser’s amber shellac I have been able to put my hand on has been devoid of a sell-by date. Hence using the can has been crap shoot.

So obviously the way to go is shellac flakes and mix my own.
A couple of questions then. When I look online for shellac I find so many types, I baulk. Is the “amber” in amber shellac just a color specification? Should I get waxed or dewaxed flakes? Where exactly do you get your shellac flakes from?
 
I have one can marked with a production date (2006!) and another I bought within the year that only has a lot number on it.

You can test whether the shellac is still good or not by putting a few drops on a piece of glass. If it gets hard, it is good, if it stays gummy, no good.

Dewaxed shellac is essential if you are top coating with something. I'm not sure whether waxed shellac might be acceptable in this case, or even desirable. It is cheaper.

Sources include shellac.net, toolsforworkingwood.com, highlandharware.com and homesteadfinishingproducts.com

One bonus of mixing your own is that you can choose your color - everything from blonde to black (anyone remember Black Jaques Shellac?).
 
The shellac cans I have used passed your test, but still seemed to have dried in a problematic way. Specifically, after the shellac was put on the first time, after 3-4 weeks the shellac alligatored a good deal. That was a couple of years ago.
I have since re-shellacked once or twice a summer.
The day before yesterday I shellacked the whole bottom and then yesterday about half the bottom.
Yesterday’s application was from a different can. This morning, after we had some rain last night, I checked and the half of the bottom was significantly discolored: much lighter in color than the section I had shellacked the day before.
So the two cans reacted in very different ways to water. The section NOT shellacked yesterday was still very glossy in appearance.
 
Staple of Saturday morning cartoons growing up!
 

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I have had this discussion with one of my canoeing friends. He felt that the issue is allowing enogh drying time between coats. Since shellac apears to dry so quickly we tend to put on multiple coats in relatively rapid succesion before the previous coat has fully cured. The delayed problem you describe seems to be consistent with this theory. Try allowing each coat to cure overnight and see if the problem reapears.
 
The section NOT shellacked yesterday was still very glossy in appearance.

Forgive me, I cannot resist...I also shellack my bottom.

More seriously, I have seen the exact result you are describing but after a week or longer paddle. With prolonged time in the water the shellack does fade and cloud. I have also had a few drops of rain land on the shellack not long (a day) after applying it and seen rain spotting.

I believe that you needed to let the boat sit longer before you let it get wet. The sections that you did a few days ago were "OK" and the bottom that you did the day before was not? That more or less bears that out.

You are already doing what I do and applying a new layer every now and then..what I do not do is start the boat with a partial can or do only a partial application. It's all or nothing. There is too much variation from can to can and even within a can if you do not stir often.It is also seemingly impossible to blend an application if part of it was done at a different time.

Ultimately none of this matters except for cosmetics. As long as you have nice fresh layer of shellack on the boat, mission accomplished.


More
 
According to "Wood Finisher's Handbook " (Sam Allen, 1984), shellac can be re-coated after four hours' drying time. It also says that it's not very water resistant (water left on the surface will cause a milky white spot).

Jeff Jewitt's book "Hand-Applied Finishes" says to let it dry 6 hours before re-coating. He also says you can test if it's dry enough by lightly scuff-sanding with 320 grit. If it powders, it's dry enough; if it gums the sandpaper, it's not dry enough.

fwiw.
 
I have been maintaining a shellacked bottom on this canoe for ten years before this, and had none of these issues before, except the standard oxidation.

Well I did wait overnight between coats, but now I am thinking there may be something else I did that accounts for the different results.
The more I have read about shellac this morning online, the more I begin to doubt my existence. Some wood finishers love the stuff, but a few contend it’s pretty much a waste of time. Zinsser’s Amber shellac is “a ready to use orange shellac,” that Zinsser calls amber because they didn’t think anyone would want orange furniture. It is not dewaxed.

Because of the shelf life problem, according to one professional woodworker, Zinsser stopped putting an explicit sell by date on the cans, substituting a manufacturing code, which, if you call Zinsser, will get you a date of manufacture.

The problem with me getting this old is that nobody makes a product the same way two years in a row, thus negating the benefit of my experience. I find a product I like and proves to me it works, and voila, it gets “improved.”
 
I have little experience with shellac.

what is the issue with shelf life?
I thought shellac was just ground up bugs or bug poop mixed with alcohol.

Dan
 
Larry, You say that after a rain the half-shellacked bottom was lighter in appearance. Was the canoe bottom exposed directly to the rain or just the humidity?
I have been shellacking the bottom of my canoes for many years now and have encountered some problems and have learned a few things but do not pretend fully to understand shellac.
In one case, after a problem with blisters under the shellac, I contacted shellac.com where I had bought my shellac flakes. He suggested that I had put the coats on too soon, ie., as soon as it felt dry at one end, I started again at the other. He suggested that I allow a minimum of 8 hours, preferable overnight between coats. I now allow 24 hours between coats and have had no further problem with blisters. He also suggested that I use 2 lb. cuts rather than 3 lb. to make thinner coats. I also now shellac my canoes in the fall rather than in the spring to allow ample drying/curing time. I do not have any problem with the shellac absorbing water and turning milky colored after a days paddle.
Having said the above, I will make a couple of observations. After a season, the shellac does alligator. Don't let it bother you. Fresh coats of shellac will make things even out and look much better. A shellac coating seems to get thinner over time, as though it sublimates. It is time to put new coats of shellac on. I generally put a minimum of three coats of shellac on when I do the bottom of a canoe.
On one occasion, I allowed my canoe to sit in the water for several days during which it rained. When I took the canoe out and emptied the rainwater, the shellac bottom had a milky appearance. I allowed the canoe to dry out on the dock inverted so as to not collect any rain, and the shellac resumed its normal orange/brown appearance. (the milkiness disappeared).
I have always used the waxed amber/orange shellac. I have no experience using dewaxed shellac on canoe bottoms. I have also used flakes and make up my 2 pound cut shellac fresh each season using a denatured alcohol that is about 95% ethanol. Some hardware store alcohols are less than 95% ethanol (like 50%) with a bunch of other chemicals. This was also the advice of the gentleman at shellac.com.
Using shellac always seems to raise more questions than answers. But, it is still much easier to renew a shellac-bottomed canoe than to repaint it. This was a feature of the Maine guides who used their canoes heavily in shallow rivers.
See you at the Assembly, where we can compare our shellacked bottoms.
Mark Z.
 
I want to correct an error. I said shellac.com. That should have been shellac.net. Sorry.
Mark Z.
 
All I can really say for sure is that for the first ten years I had a shellac bottom on this canoe, the maintenance issues were as Rollin described them in THE BOOK. That is, the shellac gradually oxidized away and could be restored easily by a fresh coat or two. The shellac I used was Zinsser’s Amber. The fresh coat would retain gloss for a period of time.

This time around the shellac is Zinsser’s Amber and it seems much more . . . finicky and sensitive.

First time around I was not even aware of the shelf-life issues, so maybe I was just lucky in the cans I bought.

This time around it seems I’m getting much more erratic results with Zinsser’s Amber. Mind you, it’s not a big deal. Last fall I shellacked before the canoe got put up in the winter. It’s stored outside in shade, but has snow fall on it. When I just went to re-shellac this week, appearance was about what I expect, that is, pretty dull.

My impression from the first ten years was that re-shellacking would somewhat dissolve the old shellac and blend with the new. Sometimes I would even just rub it over with denatured alcohol and that would spiff up the shine. Once I re shellacked and it collected a few wet leaves overnight. The wet leaves were outlined next day in the finish! This generation of Zinsser seems different, is all.

So I’m mostly just curious.

Dan, Fitz and I looked into the shelf-life issue and found that some kind of chemical action occurs after six months.

So mainly I am trying to eliminate one factor – canned premixed shellac – and see if I can get a more consistent performance.
 
The product was Zinsser's knot sealing product, which is mostly shellac. The can was old (8 years?) and the top blew off spraying the contents to some degree. I think there is a post about it on the forum, but there is a reaction that can occur with the metal in the can IIRC.

I did Larry's bottom during the last restoration. I was a little afraid that the coats were too heavy. Also no date on the dusty can at the lumber supply, so there are at least two original potential problems.

I like shellac as a sealer before varnish on the hull interior, but a few blisters show up occasionally. I wanted to try dewaxed shellac to see if I can avoid the finish problems. I have just received some dewaxed flakes from shellac.net. I will try those and see how it goes.

Fitz
 
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At my small local owner operated hardware store, the owner told me that he stopped stocking Zinsser’s Amber because demand had dropped off quite a bit. Mind you, he’s speaking from the perspective of a guy who has been operating the store for several generations. He special orders it for me. So popular demand for Amber shellac is quite limited and if the shelf life truly is six months, then the maker has quite a problem, if they have to pull the product back every six months.
Mind you, I am not even sure there is much of a problem, or if the problem is due to “old” shellac. And I am quite sure, that being a cheap SOB, I have gone ahead and used “expired” shellac time and again.
And the first time I ever laid eyes on a canoe with a shellac bottom was 25 years ago and it was a Jerry Stelmok Atkinson Traveler and it was pretty alligatored too.
The following is a very good overview by a professional restorer.
http://www.woodshopnews.com/columns-blogs/finishing/502292-shellac-as-a-sealer-its-all-just-hype
 
But he is an indoor furniture polyurethane guy! I use it because it helps blend new wood to old, two coats can go on in a day, and I use fewer coats of varnish. I think it imparts some nice color too.

I really have had none of the issues he has mentioned except an occasional blister and for all I know, that could be a varnish problem. I do want to take the wax out of the scenario and see how it goes.

Thanks, cool thread and good discussion.

Fitz
 
Yeah, different strokes for different folks.
Lest I lead anyone astray, shellac bottoms perform exactly as Rollin describes them. They are a low maintenance option for folks who don’t care to repaint their canoe bottoms a lot. It’s not paint and getting all hot and bothered about how it looks (as I have seemed to do) is beside the point.
As should be clear, I have been pretty casual about how I have cared for the bottom – using old shellac, etc. So really I have started a red herring here.
 
Straying a bit from the shellacked bottoms of canvas canoes, shellac has a history of use in canoe building. Just a quick survey shows:

Bowdish: finished boats and canoes with "linseed oil, best shellac and spar composition varnish"

Racine Boat Manufacturing Co.: for canvas canoes - "...stretched a covering of canvas, ironed into shellac and then coated with a waterproof paint"

Rushton: in early years, standard finish was 1 coat oil, one coat white shellac, 1 coat varnish. In later years, finish was one coat linseed oil, 2 coats of varnish, except two coats of white shellac would be substituted for first coat of varnish when in a hurry. Take note all of you who apply 10 coats of varnish!

It looks like this summer's project will be a reproduction of an all-wood Rushton Indian - I may just have to try Rushton's finishing schedule on it.
 
It’s not surprising. As that article states, “For about a hundred years, from the 1820s to the 1920s, shellac was the primary finish used (for all coats) by all small shops and factories.” I came across shellac as the finish on an old piano I once refinished. Now it’s uses are much more narrow. I suspect that Zinsser’s may be the only US maker supplying ready to use shellac and it’s likely a very small product line for them.
 
Several times I have run into mention of thinning shellac with lacquer thinner which supposedly eliminates the clouding problem when wet. One reference is Mike Elliot at Kettle River Canoes http://canoeguybc.wordpress.com/

I have just done a couple of coats of shellac on the interior of our canoe (prior to varnish) using his method of making up a 4 pound cut of shellac using denatured alcohol, then diluting that 1 to 1 with lacquer thinner to make a 2 pound cut. My only comment about this type shellac is that it changes it from a pleasant smell to something much worse that is also much less healthy. I plan to try this partial lacquer based shellac on my other boat that has shellac as the only gunwale finish.
 
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