Shellac flakes that won't disolve

I purchased some Hock Blonde Dewaxed Shellac flakes in April of 2009. I used a small portion of them and they worked fine. I vacuum sealed the rest in 2 oz portions to use this year. Yesterday I opened one of these vacuum sealed packages and found that the shellac had hardened into almost a solid block. I put it in a coffee grinder to make the flakes small so they would disolve better and made them very fine. I then added the necessary amount of denatured alcohol (16 oz for 2 oz of shellac for a 1 lb cut). I mixed it well a number of times last night and today. But, these very small shellac crystals are not disolving very well! They are coating the inside of the glass jar they are in and they settle to the bottom of the jar as soon as I stop shaking it.

Any idea on what the problem is? Do I need to throw these away and start over with a new batch of shellac? How do I save it from year to year if I can not vacuum seal it?

Thanks for any help on this.

Richard - I don't know what the shelf-life on shellac is but I have had stuff for a least a year that has dissolved without any problem. Not to pick on Hock but they are one of the other shellac vendors I have tried with mixed results and have had issues with it dissolving before switching to using Homestead exclusively. I don't go to te trouble of vacuum sealing my bags but I do store them in the fridge.

When I dissolve mine I:

- Use a big jar. I have a handful of 1-gallon wide-mouth pickle jars that I use.
- Stir it pretty frequently. I have found that it takes a LOT longer for it to dissolve if it is left to stand.
- I turn the jar over now and again. For times when I am not as vigilant with my stirring and it settles to the bottom, tuning it over causes small chunks / drops to fall off slowly and back into the DNA. When they all fall back into the DNA, I either stir or turn it over again to keep things moving.

Larry:

Does heat affect shellac flakes? I noticed on the Homestead web site a reference to hot weather restrictions on shipping. Mine have been stored in the workshop where it gets up over 90 degrees in the summer until I turn the AC on and then it only drops the temperature by about 10 degrees. Maybe they simply got too hot out there?

Which of the Homestead do you use? Apparently they have more than one supplier (German/Indian).

Also, if I used the Zinnzer Seal Coat, they say it is 2 lb cut. If I want to get it to a 1 lb cut how much alcohol would I need to add? (4 oz of Seal Coat at 2 lb cute plus 2 oz of alcohol = 6 oz of 1 lb cut?)

I had a few oz of shellac flakes from a different vendor that I left in the car during a hot August day. They became a solid block like yours did. THose flakes were about 1 year old. I mixed some of them up recently and it worked fine.

I suspect that you just need more mixing time. What cut are you trying to make? Mine was about 1.5#. If too thick, you might have a problem. I typically throw the shellac into a jar with alcohol, and shake it vigorously. I keep coming back every ~30 mins and shake some more. It eventually all goes in.

FWIW, even 100 year old shellac should redissolve with alcohol. The only thing heat or age might do to flakes is prevent them from hardening. But solubility should never be an issue.

I make a 1 lb cut. Does the alcohol go bad over time? The stuff I used was also from April of 2009. Maybe I should just keep mixing for a few days and see what happens.

Alcohol does not go bad. I suppose under some conditions it can oxidize to an aldehyde or acid. If that's the case, your alcohol will have an aroma that is either fruity or sour. I've used ethanol that's way older than a year - stored in a plastic bottle - before with no prob.

What kind of alcohol are you using? Denatured alcohol or rubbing alcohol. DNA is ethanol (mostly) which should dissolve a little faster than rubbing (i.e., Isopropyl) alcohol.

I have been using the Denatured Alcohol from Home Depot. It worked fine on the first batch of shellac and that is what I mixed for this batch.

Regardless of where you buy them, dewaxed shellac grades should always be refrigerated until use. What kills shellac flakes is the combination of heat+humidity. Temporary blocking (fusing together) that happens in transit is not an issue.

Jeff

Jeff:

Thanks for the hint about heat and humidity being the killers of shellac flakes. As I mentioned in my first post, I vacuum sealed 2 oz packages of the flakes when I bought them to save for later use. Is vacuum sealing a good idea? Or am I better off not doing that and simply refrigerating them in their original package?
Also, do you think I need to trash the ones I am having trouble with or should I keep shaking them for about a week and see what happens? Will I also need to strain them before use if there is still some residue?

Vacuum sealing probably has little effect because oxygen isn't involved to a great extent in the degradation process. A constant cool temperature is your best weapon. In addition once the flakes go, it's best to trash them.

Vacuum sealing would certainly help with humidity changes.