Wednesday, December 14, 2011

Shellac Gone Gummy

I had encountered shellac gone bad before, but I had never come across shellac that won't dissolve completely in denatured alcohol.

I mixed up a batch of blonde shellac but, days later, it looked like semi-masticated lemon jello rather than clear finish.

I mixed another batch using amber flakes to see if the alcohol was the problem, but they dissolved completely in an hour.

I had used flakes from the blonde bag before. I couldn't understand why they would have gone bad because they were always stored in a cool, dry shop.

A quick google search led me to a blog post written by Joel Moskowitz, so I emailed him to ask his opinion.

He told me that the flakes had oxidized and that they should have been stored in an air-tight container (rather than in the original plastic zip-loc bag).  He also suggested that I try pulverizing the flakes, but I had already tried that and it didn't seem to help.

Today I bought a brand new bag of blonde flakes and immediately poured the contents into a glass jar with screw-on lid.

So, if after 24 hours your newly mixed batch of shellac still looks like gatorade-doused caviar, you know what to do.

14 comments:

Jonathan P. Szczepanski said...

Are you sure Nancy didn't use the bag to blow her nose in?

:-)

Jonathan
=============================

Kari Hultman said...

Gah!

Eric said...

Thanks for the tip Kari.
It helps when I'm trying to squeeze out every $ worth of the supplies I have.

Kari Hultman said...

Believe me, Eric, it was painful throwing out that half full bag of $40 shellac flakes. I'll never make that mistake again.

Tico Vogt said...

I find it easy to work with Zinzer shellac, buying a small can and thinning it with denatured alcohol in a jar. Never any problems.

Mark Hochstein said...

I put mine in a glass jar and spray Bloxygen in before sealing it. I try to keep the O2 away just like liquid finishes. Seems to work or me so far.

Wilbur Pan said...

Did you throw out all of the bad shellac? If you have some left, I'd like to take a crack at it.

Kari Hultman said...

Tico, the premixed stuff works great. I can never seem to get through the entire can quickly enough so I end up throwing too much out.

Mark, I tossed in a bag of desiccant. Hopefully it will help. I wonder if laying a large sheet of plastic wrap in the jar—on top of the flakes and coming out of the top of the jar—so it's sealed with the threads of the lid would displace the oxygen. ??

Wilbur, email me your address and I'll send it to you. goodwoodworkshop@comcast.net

thekiltedwoodworker said...

Kari,

I buy my shellac from Vijay @ Shellac Finishes (http://www.shellacfinishes.com/) and have done so since 2005 or so. You can buy smaller portions (.5 lb or even a sampler pack with 4oz bags, which would be good for a woodworker who doesn't make as many things in a year and wants to try the different varieties of shellac).

I store mine double bagged in ziploc freezer bags in a box on a dark shelf in my basement and haven't had a problem yet. My basement is very dry, too, so that probably helps.

If you haven't bought anything from Vijay before, you should definitely check him out the next time you're ready for more.

Ethan

alejandro moreno said...

I'm not a chemist but I've been cabinetmaker for fifteen years and used shellac often. Maybe this article could be useful http://chemistry.about.com/b/2009/03/16/what-is-denatured-alcohol.htm Maybe the denaturalizing agent/s aren't the appropriate/s. Did you use the same alcohol before? It sounds to me like containing some water (just guessing after reading the article). I hope it helps.

Anonymous said...

Kari,
I have had the same problem. Bob Flexner's book on finishing says that it is the agents used to bleach the blonde shellac that give it a shelf life. The amber and garnet flakes will keep forever.

I have had blond shellac flakes last for years and some that went off fairly quickly. You never know how long it has sat around before you buy it.

Putting it in a jar sounds like a good idea. I have to resist the temptation to try to break it up in the bag. That makes small holes in the bag that let the air in :)
Karen

Kari Hultman said...

Thanks for the recommendation, Ethan. :o)

Alejandro, thank you for the link. I'm using the same alcohol as always—just a can from the local big box store—but I have heard others suggest that using a better quality denatured alcohol might help.

Karen, I didn't know that about the bleaching/shelf life, but it certainly sheds light on this situation. Thank you!

Mark Banninga said...

I've had shellac finishes ruined a couple times on pieces of furniture. Once the glue that held the felt on the bottom of a lamp base dissolved a ring on a table. I have moved to using natural oil varnish, or rubbed varnish oil finishes on my projects.

I enjoy reading your blog, my work does not allow me to take the time to do everything with hand tools alone, so it's refreshing to read your blogs.

Anonymous said...

http://www.leevalley.com/en/shopping/TechInfo.aspx?p=44330

"In addition to lightening shellac, the refining process also affects the shelf life of the product. The more refined the shellac, the shorter its shelf life.The most highly refined forms (blonde and white) seem also to be less durable than the other grades."

I prefer the Orange shellac flakes both for their finish color as well as their shelf life.

Chuck