1704 Varnish Question

[FiddleBasher]

I am in the process of making 1704 varnish. When it's finally ready i guess it will start to deteriorate. As most products have a use by date. What's the estimated shelf life? One year, six months!!!

[David Burgess]

14 minutes ago, FiddleBasher said:

I am in the process of making 1704 varnish. When it's finally ready i guess it will start to deteriorate. As most products have a use by date. What's the estimated shelf life? One year, six months!!!

In my experience, the shelf life highly depends on what sort of alcohol solvent you use.
Pure ethanol: long shelf life.
Ethanol denatured with methanol: reduced shelf life.
Methanol: Worst shelf life of those I have experimented with.

But there's another hugely significant factor, and that is the way the shellac is processed in the first place. Some I've tried have significantly gone downhill before I ever dissolved them, or even before I purchased them. The best I have used remained quite stable for over two decades, prior to my dissolving them in alcohol. I still haven't discovered the time limit for these.
 

[FiddleBasher]

Thank you David, if the varnish has "gone off" what would happen if I used it?

[Shunyata]

If the mixed shellac is too old it never dries or hardens.

[Davide Sora]

4 hours ago, FiddleBasher said:

I am in the process of making 1704 varnish. When it's finally ready i guess it will start to deteriorate. As most products have a use by date. What's the estimated shelf life? One year, six months!!!

When dissolved in alcohol, shellac undergoes an esterification process which gradually makes it softer, until it transforms into a gummy substance that never hardens completely. The shelf life, as David Burgess says, depends on several factors such as the quality of the starting shellac (treated, raw untreated), the type of alcohol used, and the environmental conditions. In my experience, using raw untreated shellac and food-grade ethyl alcohol, after six months there are no significant changes, after a year it is perfectly usable but will be a little softer and a bit more elastic, after a year and a half it would still be usable but it starts to become too soft for my tastes, after two years I consider it unusable, except for small touch-ups such as small chips. I don't use exactly the 1704 recipe, but my varnish contains alcohol and shellac and has the same problems and behavior over time, so I avoid making large quantities to use it all within a year. If I have small quantities left over, especially colored varnish which also contains precious pigments, I add it to the new colored one I make, but it must not be a predominant quantity.

[FiddleBasher]

17 hours ago, Davide Sora said:

When dissolved in alcohol, shellac undergoes an esterification process which gradually makes it softer, until it transforms into a gummy substance that never hardens completely. The shelf life, as David Burgess says, depends on several factors such as the quality of the starting shellac (treated, raw untreated), the type of alcohol used, and the environmental conditions. In my experience, using raw untreated shellac and food-grade ethyl alcohol, after six months there are no significant changes, after a year it is perfectly usable but will be a little softer and a bit more elastic, after a year and a half it would still be usable but it starts to become too soft for my tastes, after two years I consider it unusable, except for small touch-ups such as small chips. I don't use exactly the 1704 recipe, but my varnish contains alcohol and shellac and has the same problems and behavior over time, so I avoid making large quantities to use it all within a year. If I have small quantities left over, especially colored varnish which also contains precious pigments, I add it to the new colored one I make, but it must not be a predominant quantity.

Thank you Davide is treated shellac the type in  flakes? I have sticklac which I know is the natural thing, plus seedlac which I'm not sure how that is classified.

[jefcostello]

Sticklac is knocked off a tree branch. Heat it and make it into granules. It's called seedlac. Strain them again, stretch them into long strips, and flatten them with a small piece, called buttonlac.

https://www.youtube.com/watch?v=eqMuFY-6aTA

On 2023/12/16 at AM12點09分, FiddleBasher said:

謝謝大衛，紫膠經過處理後是片狀的嗎？我有 Sticklac，我知道這是天然的東西，還有 Seedlac，我不確定它是如何分類的。

 

[Davide Sora]

On 12/15/2023 at 5:09 PM, FiddleBasher said:

Thank you Davide is treated shellac the type in  flakes? I have sticklac which I know is the natural thing, plus seedlac which I'm not sure how that is classified.

As Jefcostello says.

I use sticklac and seedlac that are equivalent in degree of purity (in the sense of not chemically treated). The buttonlac is also supposed to be not chemically treated, but I've never used it so I don't know how it performs over time. The problem is the dewaxed types, often not by simple filtering but by much faster chemical treatment, and the decolored types, which are chemically bleached. These treatments cause some modification to the structure of the shellac which makes it insoluble over time. I had to throw away about 1 kg of shellac (in flakes) because after two years of aging (not dissolved) it no longer dissolved in alcohol. Dewaxed and bleached shellac no longer dissolves after a year or two in my experience, so if you need them do not buy too much.

[Salve Håkedal]

I've had dewaxed and bleached shellac (from Kremer) for quite a few years that still dissolves well in alcohol. Once dissolved, however, the shelf life is short. (Therefor, I make it fresh for every new fiddle.)

[jefcostello]

1 hour ago, Davide Sora said:

As Jefcostello says.

I use sticklac and seedlac that are equivalent in degree of purity (in the sense of not chemically treated). The buttonlac is also supposed to be not chemically treated, but I've never used it so I don't know how it performs over time. The problem is the dewaxed types, often not by simple filtering but by much faster chemical treatment, and the decolored types, which are chemically bleached. These treatments cause some modification to the structure of the shellac which makes it insoluble over time. I had to throw away about 1 kg of shellac (in flakes) because after two years of aging (not dissolved) it no longer dissolved in alcohol. Dewaxed and bleached shellac no longer dissolves after a year or two in my experience, so if you need them do not buy too much.

I put the prepared shellac liquid in the storage room. The previous summer, the temperature was as high as 36C, and then my ethanol shellac went bad, (a bit like a cake?)

I don't know how long it lasts once dissolved, but I suspect high heat will spoil the shellac.

The color of seedlac is very beautiful. If you don't heat it, the bottom is a pile of debris (1/4), the middle is 1/2 fat, and the top is a transparent orange liquid. Use 1:3.3 (weight: alcohol volume)

I suspect it’s the secret of Mr. Sora’s beauty

[Michael Richwine]

In the USA, I've had really good results over the last umpteen years with the guys at shellac.net. they have a wide selection of shellac products, as well as varnish and touchup supplies.  I make my touchup varnish in small batches, and test every couple of months after 6 months. After I switched to 190 proof grain alcohol for a solvent, I quit having to throw out unused leftovers.

[Davide Sora]

13 hours ago, Salve Håkedal said:

I've had dewaxed and bleached shellac (from Kremer) for quite a few years that still dissolves well in alcohol. Once dissolved, however, the shelf life is short. (Therefor, I make it fresh for every new fiddle.)

I think the main problem is that the producers do not declare the type of treatments to which the shellac has been subjected, so it is not possible to generalize about its behavior, we just have to do our tests to try to understand and choose accordingly.