Exploding Shellac

[BobW]

Yesterday I pulled an unopened quart can of Zinsser Bulls Eye Shellac out of my paint cabinet.  It had been purchased a little over a year ago, and I know that liquid shellac has a shelf life so I was going to test it to see if it was still good before using it on my project.  I noticed that the bottom of the can was kind of puffed out.  If it had been a can of peas, I would have immediately thrown it out, but I wasn't planning to eat it so I proceeded.  As I started prying the lid off, I was startled by a very loud pop, and the lid slammed into my thumb and then flew across the room.  Has anyone else experienced this?  I tried the shellac on a test piece, and it hardened, so I guess it's ok to use.

Zinsser used to print the production date on the can, but now they just put a lot number.  Is there a date code in that number, somehow?

[jteneyck]

Yesterday I pulled an unopened quart can of Zinsser Bulls Eye Shellac out of my paint cabinet.  It had been purchased a little over a year ago, and I know that liquid shellac has a shelf life so I was going to test it to see if it was still good before using it on my project.  I noticed that the bottom of the can was kind of puffed out.  If it had been a can of peas, I would have immediately thrown it out, but I wasn't planning to eat it so I proceeded.  As I started prying the lid off, I was startled by a very loud pop, and the lid slammed into my thumb and then flew across the room.  Has anyone else experienced this?  I tried the shellac on a test piece, and it hardened, so I guess it's ok to use.

Zinsser used to print the production date on the can, but now they just put a lot number.  Is there a date code in that number, somehow?

Nope, never had a can full of pressure, but I have had two or three leakers, one of which let at least a quart out onto my bench and ruined several drawer box parts. 

Someone here or on SMC posted the key to deciphering the Lot number, but I think it has changed yet again because when I recently tried to do it it made no sense. 

Premixed shellac is great stuff, but the only way to avoid leaks, etc. is to transfer it into glass jars, or to at least set the can inside a plastic pail to catch the leak should it happen.  That's what I try to do now.  

John

[fredhargis]

I have not seen that (the can problem) and wonder if it had been subjected to high temps or whatnot. Beyind that, if it dried I'd use it...but maybe get in contact with Zinnser about it. As for the code date, Flexner figured it out.  Here's what he said about reading the lot # stamp on the can:
Here is how to read the stamp.

• The first letter “S” identifies the plant that packaged the product. In the case of the two cans shown, it was Somerset, NJ.
  
• The first number is the last digit in the year the shellac was packaged.
  
• The second number is the month. For October, November and December the first letter is used instead of a number: “O,” “N,” or “D.”
  
• The third and forth numbers provide the date within that month.
  
• The fifth number or letter indicates the “run” on that date.
  

That whole article is here.

[BobW]

I have not seen that (the can problem) and wonder if it had been subjected to high temps or whatnot. Beyind that, if it dried I'd use it...but maybe get in contact with Zinnser about it. As for the code date, Flexner figured it out.  Here's what he said about reading the lot # stamp on the can:
Here is how to read the stamp.

• The first letter “S” identifies the plant that packaged the product. In the case of the two cans shown, it was Somerset, NJ.
  
• The first number is the last digit in the year the shellac was packaged.
  
• The second number is the month. For October, November and December the first letter is used instead of a number: “O,” “N,” or “D.”
  
• The third and forth numbers provide the date within that month.
  
• The fifth number or letter indicates the “run” on that date.
  

That whole article is here.

That's very good information!  The code on my can is S2612A D, so it was manufactured June 12, 2012.  I know I bought the can late summer 2016, so it was sitting on a shelf somewhere, before I got it, for over four years!

BTW, regarding high temps, my shop has A/C and heat, although it is turned off if I'm not going to be there.  I also have a high/low thermometer, and the temp range for the last two years has been, high: 84F. low: 60F.

Thanks for the replies