failure modes of shellac


I'm working on a repair of an old table. the wood is mahogany, the real stuff. the finish is shellac. I did the repair to the wood parts and started into the finishing.
I mixed up a batch of shellac from some garnet flakes I had, but it didn't completely dissolve. the liquid turned the right color, but the partially softened flakes remained floating around in it, and a test drop of it remained gummy for days. so off to the store to buy another $25 ounce of bug spit.
got the new stuff. mixed up a batch. it was completely dissolved in under an hour. all's good, on with padding. got a few rounds padded on last night and went out. got in late, went to bed. got up this morning, went out to the shop. the surface was nice and hard, so I proceeded with another round. went well, and as I was closing up the pad in a ziplock baggie and putting the parts in order I noticed that the jar of shellac has what appears to be solids settling out in the bottom. hmm... a shake... no change... get a stir stick and give it a poke. it's like a mass of stiff jelly at the bottom of the jar. I got it free of the jar bottom and shook it some more, but it doesn't seem to be wanting to go back into solution.
what gives? was I just way wrong on my mix proportions? I just sort of guesstimated, an inch or so of flakes in the bottom, the jar full to about 3 inches with alcohol. I even went and bought a fresh can of alcohol for this one...
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snipped-for-privacy@all.costs wrote in
<snip>

Whose shellac are you buying? I've never had a problem with the material from Jeff Jewitt, Ron Hock, or the late attempt at worldwide market domination that was Paddy O'Deen's quest...
Patriarch
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On Tue, 19 Jul 2005 13:14:22 -0500, Patriarch

behlen.
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On Tue, 19 Jul 2005 09:33:14 -0700, snipped-for-privacy@all.costs wrote:

Could it be wax?
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Chuck Taylor
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On Tue, 19 Jul 2005 13:58:18 -0500, Chuck Taylor

I'm thinking it must be. the can didn't say dewaxed, and the product I used off of the top performed fine. the last batch I bought, that finally expired in the shop after a couple of years of storage, was dewaxed from ron hock. it didn't have anything settling out on the bottom.
thing is, I'm no expert on shellac- I didn't know what to expect the wax to look like. I didn't expect it to look like jello.
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snipped-for-privacy@all.costs wrote in wrote:

If it didn't SAY dewaxed, there's little reason to believe that it is.
If there is to be no top coat, waxy shellac is just fine.
Or you can decant it, by carefully pouring the clearer top liquid off into another container.
There are uses for the shellac wax, but at this hour, I cannot remember what they are, or if they have application in woodworking. Woodturner's friction polish, perhaps?
Patriarch
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Patriarch wrote:

Not long ago I noted a label on some fruit inthe grocery store that said it had been sealed with shellac wax. I had heard of wax being used on fruit before but always assumed it was paraffin.
I do not recall what sort of fruit, maybe apples. The object of the waxing, I suppose, is to reduce dehydration or to shed beads from condensation to reduce mildew on the skin. Apples will keep fresh for months stored in CO2.
--

FF


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snipped-for-privacy@spamcop.net wrote:

For fruits that have been treated with applied pesticides, the washing-off process degrades the protective ability of the skin significantly. The shellac wax is applied to help preserve the fruit and has the added bonus of making them shiny and appealing to those attracted to shiny objects.
Shellac wax is really hard stuff, comparable to carnuba wax. I still have about a millenium's supply from when I used to sell this stuff (my goodness, I realize I've been outta that biz for 4 years and there are still a handful of youse who remember). I mix it with turps and beeswax and use it primarly for waxing handplaces, saws, auger bit lead screws, etc.
O'Deen
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I was beginning to think you had gone on a 12 step program, regarding the wReck.
Welcome back, Paddy. We've been missing your experience & wit.
Patriarch
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snipped-for-privacy@all.costs says...

How sure are you that it was dissolved? Even in hot weather I can't imagine it dissolving in an hour. My guess is it wasn't dissolved and that is what you are seeing.
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On Tue, 19 Jul 2005 21:48:26 -0500, Hax Planx

it didn't show up until the next day. the shellac really did dissolve in roughly an hour....
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snipped-for-privacy@all.costs says...

It sounds impossible to me, even if it was a 1/2# cut. It took two days for a 2# cut to dissolve for me with the average temperature over 90 and I shook it every time I remembered. It really couldn't be anything else. The undissolved flakes do turn into a mass of goo on the bottom and I think you just didn't notice it at first.
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I'm like you...there are times when I've shaken the living dog poo out of the container and it still turns to goo anyway...that's why I typically mix my shellac a week or so before I think I'm going to need it.
Maybe I'll start mixing mine in a blender...
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On Tue, 19 Jul 2005 09:33:14 -0700, snipped-for-privacy@all.costs wrote:

snip
Sounds most odd, never heard of that before. The mix sounds fine, but I normally give it a chance to dissolve overnight if possible.
Sounds like contaminated shellac. Get a small quantity of another batch and/or from another supplier to try. What alcohol are you using? I use either industrial ethanol (96% ethanol, 4 % methanol) or else pure methanol, but the latter is a bit toxic, so I only use it outdoors.
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Barry Lennox wrote:

thing is,otherwise it's performing just fine. what I gather from the ancient scripts is that if something is wrong with the shellac itself it never dries... just gets gooey. what I applied to the table has dried nice and hard and has done it nice and quickly... it sounds like a good batch.

the stuff from the paint store labelled shellac thinner.

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I always grind my shellac flakes in an old coffee grinder and still have a little particulate matter after dissolving and I filter it before use. Maybe it dissolves better if ground finer. Hope that helps.
MBR
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That jelly is nothing more than undissolved shellac.
When you're dissolving shellac, you have to shake it periodically to prevent this. Otherwise it will happen most of the time. And the wax content has nothing to do with it...I always used de-waxed, and this happened to me plenty of times before when I forget to shake the jar.
The clump at the bottom of the jar *will* eventually dissolve, but it will take as long as a week to do so.
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wood snipped-for-privacy@yahoo.com wrote:

good to know. it's a bit disconcerting, because the mass in the bottom is _slightly_ more volume than the dried flakes I started with. sounds like it has absorbed some alcohol and expanded. if that was wax it would be a _lot_ of wax.

I did shake. unfortunately, garnet is dark enough that it's easy to miss something like this going on in the bottom of the jar, and the jelly is sticky enough that once it settles it kinda isolates itself- it doesn't float around and get agitated, and only has one surface in contact with the liquid on the top.

good to hear.

I dropped a machine nut into the jar to act as an agitator to help break up the mass when shaking, plus I'm doing a little stirring as well.
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I can't understand why you bug-parts guys don't invest in a stirring hot plate. You can pick them up fairly cheaply on eBay ($25 and up) although plain magnetic stirrers are more common. Put your alcohol in a flat bottomed jar, drop in the bug parts and a teflon covered magnetic bar and close it up. Turn on the stirrer and come back when it's done.
That's what I plan on doing if I ever get my damn bookcase finished.
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satisfying as that made by the Arts and Crafts movement in the early years
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Ed Clarke wrote:

you know, I've wanted one of those for years. the last time I looked at them was before ebay and the new price was way out of my budget. I had kind of given up, though I have kept an eye out at auctions and such. knowing that I can get one on ebay so inexpensively, I will do just that. thanks for the heads up.
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