Can of Shellac blew up today

R

rekit

Joined
Jun 30, 2018
Messages
536
Location
TX
I'm sure most of you guys do some woodwork too, want to pass this along. Replacing some rotten pine siding and went to open a small pint can of maybe 2 year old Shellac to seal a few knots before priming the wood. Pryed off the lid and it went off like a shotgun. The lid hit my hand so hard it cut a small gash, and that "stuff" went every where. I'm amazed the can and lid held that much pressure. Temperatures were 60 last nite, 78 today. Can was in the garage on a shelf in the dark. So glad I had my glasses on. Never thought I would need them to open a can of paint. And the Shellac was still good I guess, not hard.
"Shellac is generally made from two ingredients, raw seed lac and ethyl alcohol." Made from bugs, hmmm.
 
You mean, you didn’t know the ingredients of shellac prior to this?

The only possible explanation I can come up with is a buildup of alcohol vapor under the lid in a partially used can and some sort of spark when you pried the thing off.

I’ve never heard of this sort of thing happening, but I will be certain to wear my safety glasses when I open cans!
 
Astro14 said:
I’ve never heard of this sort of thing happening, but I will be certain to wear my safety glasses when I open cans!
Click to expand...
I had a can of automotive epoxy primer blow open on the back seat of my car once during a very hot spell in the summer. That made a mess that was never able to be cleaned up. I am surprised such a thing happened at 78 degrees, why wouldn't that happen with every can in the hardware store?

And yes lac resin is used in a lot of things and is quite useful.
 
kschachn said:
I had a can of automotive epoxy primer blow open on the back seat of my car once during a very hot spell in the summer. That made a mess that was never able to be cleaned up. I am surprised such a thing happened at 78 degrees, why wouldn't that happen with every can in the hardware store?

And yes lac resin is used in a lot of things and is quite useful.
Click to expand...
probably depends on the vapor pressure of the propellant in the can..it can be 150 to 170 degrees inside a car on a hot day.
don't know what they were using for propellant in your case but maybe it was old school propellant, back when they used cfc's.
edit... just went and checked, they used to use R11 in aerosols back in the day... 150 degrees F has a vapor pressure of 40 psi for R 11. so it is possible,
 
Last edited:
Astro14 said:
You mean, you didn’t know the ingredients of shellac prior to this?

The only possible explanation I can come up with is a buildup of alcohol vapor under the lid in a partially used can and some sort of spark when you pried the thing off.

I’ve never heard of this sort of thing happening, but I will be certain to wear my safety glasses when I open cans!
Click to expand...
No, I didn't. I kinda assumed it had to do with turpentine for some reason.
 
MSCH said:
probably depends on the vapor pressure of the propellant in the can..it can be 150 to 170 degrees inside a car on a hot day.
don't know what they were using for propellant in your case but maybe it was old school propellant, back when they used cfc's.
edit... just went and checked, they used to use R11 in aerosols back in the day... 150 degrees F has a vapor pressure of 40 psi for R 11. so it is possible,
Click to expand...
No it wasn’t a spray can, just one of the two parts in a quart can.
 
MSCH said:
OK, maybe the contents separated and the same effect.
Click to expand...
No not really. This was a two-part epoxy primer and it was the solvent pressure due to the heat. One part is clear and the other is pigmented, it was the pigmented half that came open. It had to be upwards of 120 degrees inside on that day.
 
There's a lot of stuff that can go boom or go poof. Just try drying out deck stain on rags. Linseed oil creates heat when it dries. Not generally a problem if it's laid out and can cool, but once a neighbor just stuffed them in empty cans of deck stain to dry, and that trapped in heat. Fun times. I only say that because nobody got hurt.

 
I once had a small can of Mechanics brand carb cleaner blow it's top. Dropped the parts from a Datsun 510 carb into the basket, closed the top and gave it a minute of some gentle swirling agitation. A few minutes later the top blew off.
 
OP here. I did shake the shellac can before I opened it, pretty good too. Shoulda stirred? I'll never know.
 
I've got two cans of old spray paint completely full and pressurized but the internal valve is clogged and it it won't spray. Waiting for a big bonfire......
 
Astro14 said:
You mean, you didn’t know the ingredients of shellac prior to this?

The only possible explanation I can come up with is a buildup of alcohol vapor under the lid in a partially used can and some sort of spark when you pried the thing off.

I’ve never heard of this sort of thing happening, but I will be certain to wear my safety glasses when I open cans!
Click to expand...
That's all i can see happening too. I've mixed my own shellac with flakes and denatured alcohol, which had methanol . Was the lid or any part rusty? What did you pry off the lid with? Maybe the steel of the implement and the lid of the can sparked and lit off the alcohol vapor.

Shellac should be less volatile than lacquer. Real nitrocellulose lacquer is extremely flammable.
 
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