Do Shellac Flakes Have A Shelf Life?

[Lawren5]

I purchased a bag of shellac flakes off eBay and cannot get them to melt. Instead, they just get a little soft and sticky but won’t form a string when pulled from the pallet warmer. Applying more heat just makes them crisp up. I’ve seen several of Mark’s videos in which he heats up shellac and it melts nicely but I’m not getting the same results.

Is it possible that I’ve got a bad batch of flakes or is it something else that could be causing this? Would it be better to use a shellac stick instead of flakes?

[Mark]

Very interesting you should post this. I was thinking the same thing.
Off camera I started with my shellac flakes which I prefer but I had the same problem. Soft but not melting - was quite frustrating. Changed over to the stick and it was perfect. I have a huge bag of flakes but I fear they are now useless. Fortunately its not an expensive product.

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[Lawren5]

Thanks, Mark.

As an amateur watch repairer, it's good to know that it's not just me. I'll order some new shellac in stick form.

[saswatch88]

I act always preferred stick form. But good to know Just in case I ever decided to go to flakes

[CaptCalvin]

I don't have any experience with shellac bought in flake form but I am curious what would happen if you reconstituted them into a big mass. Bunch all of them together and heat them up. If this is successful perhaps the shellac can be used after all.

[AndyHull]

I suspect they may be adulterated with "something". Try dissolving them in denatured alcohol, mentholated spirits or isopropanol and then evaporating the alcohol off. Any other "stuff" may separate from the shellac. The flakes may be intended for french polishing, in which case the "stuff" may be some form of wax, which typically would not dissolve in alcohol.

[oldhippy]

I'm wondering if it how they are kept or what are they kept in. I had mine in a small wooden draw and never had any problem. 

[StuartBaker104]

Well that question got me googling...

There is a lot of discussion about this on the ”interweb”, but mostly in relation to woodworking and nail polish!

Shellac is a natural product, subjected to various purification processes prior to sale which have changed significantly over the years, so firstly, the shellac we buy today is likely to be much purer and more consistent than in the past.

Shellac flakes sold for making wood finishes definitely deteriorate with age. After a period of time the can no longer be dissolved in alcohol. I haven’t found out exactly why, but moisture, heat and light are all cited as causes. So, keeping your flakes in a sealed dark container would be a good thing.

Shellac in stick form will have a lower surface area for a given volume and therefore certainly less susceptible to moisture.

Once mixed with alcohol, shellac will start to react chemically, (search for esterification if you want to know more), and evaporation of the alcohol doesn’t get you back to where you started. This is why pre-mixed shellac varnishes have a short shelf life.

Shellac is chemically similar to acrylic, and hence made of long polymer chains. I’ve read conflicting information about whether these will cross-link in ultraviolet light (the process that causes unbreakable watch crystals to go yellow and brittle). However, I would expect it to behave in a similar way - again, this is a non reversible reaction.

All of this may go some way to explain why some people reprt there is no problem with cleaning pallets in alcohol and others saying it softens the shellac.

I’m now into this deep enough to need a good chemist to get me back out. Any volunteers?

 

[oldhippy]

So keeping them in a small dry draw in a cabinet which is  dark works. 

[jdm]

10 hours ago, Mark said:

I have a huge bag of flakes but I fear they are now useless.

Shellac is never useless Mark . From small drawers to large antique cabinets it's a lovely and rewarding material to work with. 

6 hours ago, AndyHull said:

The flakes may be intended for french polishing, in which case the "stuff" may be some form of wax, which typically would not dissolve in alcohol.

Yes, there are many varieties of flaked shellac, from the most common raw which may even contain pitch, to low wax, to wax free, which is clearer and more resistant to humidity. To remove wax from shellac dilute in alcohol 50% leaving it a week, then seep with paper filters.

Edited December 15, 2019 by jdm

[clockboy]

Wow thats interesting I have a bag of flakes as well. BUM

[teegee]

On 12/15/2019 at 8:14 AM, Mark said:

Off camera I started with my shellac flakes which I prefer but I had the same problem. Soft but not melting - was quite frustrating. Changed over to the stick and it was perfect. I have a huge bag of flakes but I fear they are now useless. Fortunately its not an expensive product.

The sticks that Cousins sells are really nice for work-cementing etc and work really well to set pallets, but that type dissolves in naphtha, which I use as a rinse. They sell a light coloured a dark coloured stick; I've only tried the light one.

Another type of shellac from cousins is shaped like large blobs, but that's more of a course pitch-like cementing variant that is useless for small work because of the amount of filler material in it. I have another big bar of shellac of unknown origin, which is useless for the same reason.

In the end I got some old shellac flakes from my friend, and they work excellent. No idea where they came from or what type it is, but my one teaspoon of lucky flakes will set a lifetime of pallets.