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Can anyone help with shellac mixing problem?
I’ve French polished a few instruments, or parts of them, with a reasonable amount of success, but I have problems when mixing a new solution. I use the Stewmac flakes and 95° alcohol. Working from the Milburn tutorial I try to mix a 1lb cut. As I’m English but live in France, we don’t have pounds and ounces or gallons even though I know what they are, and anyway US gallons aren’t the same as British ones (go figure!), so I worked out the proportions and calculated that for a 1lb cut I’d need to dissolve 24 grammes of flakes in 200 ml. of alcohol.
Milburn (and Stewmac) say it dissolves easier if you whizz the flakes in a coffee grinder so I did that. I also put my jar in a pan of hot water because that should help too. I’ve been stirring it and warming it for a week now and it still looks like this. The cloudy part at the bottom is the undissolved granules. You can also see them stuck to the sides further up from when I stirit.
Any polite suggestions as to what I should do with it?

Find yourself a magnetic stirrer. Many online are laboratory grade with hot plates, but you can find basic battery or usb powered ones on Amazon for cheap. One of those will dissolve your shellac in an hour or so.

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Craig

Are you sure thee cloudy part at the bottom is undisolved? It looks like wax to me.

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Jim Watts
http://jameswattsguitars.com

What brand is your shellac flakes and how old? Is it waxed or dewaxed?

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I saw a post I think from Alan Carruth where he recommended using a loose leaf tea bag suspended by a toothpick just barely touching the alcohol to dissolve the flakes. Never tried it though…

I would decant off some of the top liquid and test it to see how well it dries. If the flakes are too old, what does dissolve may not dry well.
You could run it through a coffee filter to filter out some of the wax and impurities and then try adding more alcohol to try to dissolve any remaining shellac.

I've read the more highly processed (lighter colored) flakes go bad sooner than the darker less processed stuff . I've had them go bad after a year.

Hi, Dave! Like Jim said, it looks like wax. I'd try another source of flakes that sells a lot of shellac. The majority of SM customers don't do FP shellac (not to disparage SM at all or their customers—myself included), so their stock might not be the freshest. Try someone like shellac.net, whose stock probably moves more quickly. I've had good luck also with VJay's shellac at shellacfinishes.com or woodfinishingenterprises.com

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formerly known around here as burbank
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http://www.patfosterguitars.com

It's Stewmac, dewaxed, but it is old, perhaps 10 years or more but I thought if it was in an airtight container it should be OK.


In fact I used the last of my previous mix 6 months ago on the front of this, and it worked OK



I don't think it's wax. As I said, I ground it into granules and some of them seem to have softened but not fully dissolved


I'll see if those things are available over here. I'd never heard of them.


Hi Pat, as I said, it might have been fresh when I got it but that was a long time ago. As I only make one or two instruments a year which don't always involve FP and getting stuff from the US gets more and more expensive, it all gets a bit problematical

I just recently had to buy a new batch of shellac because of (what appears) to be the same problem as you are showing. My shellac was about 5 years old and wouldn't completely dissolved even though I kept it in a dry cool place. The new batch dissolved within a couple of hours.

I would say your shellac is past its prime.

Bob

Surely you can get shellac for “French polishing” in France
Beautiful bass btw.

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Jim Watts
http://jameswattsguitars.com

Nice bass!

It is not wax. The flakes are dewaxed blonde. What is at the bottom is partially dissolved shellac that's forming a gel. I think the culprit is 10 year old blonde flakes. Lesser refined grades of lac seem to have longer shelf life.

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Stay with the happy people.
--Reynolds Large

Yep, time to buy some new flakes. You can strain off the gloop and use the rest, but it probably won't get as hard as fresh. I always buy small quantity, 4oz at most. Guitars use so little, even though it's more expensive per pound, you save in in the long run due to less waste. I usually buy from shellac.net or WellerMart.

95° alcohol or 95% alcohol? 95° proof alcohol is only ~47% alcohol, with most of the rest being water.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

"Any polite suggestions as to what I should do with it?"

Hi Dave a couple points from me if I may please.

If you google "how long do shellac flakes" keep what was just returned to me was about 3 years provided that it's kept in the dark in a proper container.

So there is that.

I would be more interested in the alcohol that you are using. We never use denatured alcohol and instead use the 180 - 190 (forgetting the exact proof) proof ever clear sold in some states in the US. It's moonshine and will dissolve anything including marriages.

I was told that flakes overheated during shipping are difficult to dissolve. Got a refund. They sat undissolved for a month.

I use 24 g in 100 ml for my 2# cut, so your calculation of 24g for 200 ml for a 1# cut is ok.
It does take a few days to fully dissolve with occasional stirring.
I think Trevor is right, you are probably not using 95% alcohol.

Thank you for your replies everyone. I think, from what some of you have said (having the same problem) that it must be that the shellac flakes are too old. I bought them so long ago I can't even remember when it was!
I think the alcohol is actually 95% although the bottle is marked 95°. The French have a habit of talking about "wine at 14degrees of alcohol" or "whisky at 40 degrees" when what they mean is %.
I've found a French supplier on line who has 'Super blond dewaxed shellac' and 'Ethyl alcohol at 98%'. They also have isopropyl alcohol at 99.5%. Does anyone use that?
https://www.art-chimie-online.com/gomme ... ciree.html
https://www.art-chimie-online.com/produ ... 2h6o-.html
https://www.art-chimie-online.com/produ ... panol.html

I use the IPA due to unavailability of Ethyl alcohol in UK, although remember it is a bit more hazardous to health.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I use 90% isopropyl because it is easy to find, buy, it works, and it is cheap.

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Why be normal?