BLO (& others) = Spontaneous Combustion

[Doug Hobkirk]

A pile of rags that have been used to apply or wipe off BLO are combustive. I put them outside spread out on a gravel driveway, each one weighted with a rock, and wait for them to dry completely before I dispose of them. Or I burn them. I further protect myself by using very little BLO - only in my David Mark's (or was it originally Sam Maloof's?) finish of 1/3 each BLO/Tung Oil/Poly. Most other finishing rags I simply spread out on the rims of my in-shop trash cans.

1. But do other oils and varnishes spontaneously combust?
2. Is real tung oil much safer and therefore a practical alternative to BLO (although I believe tung oil has a longer cure time)?
3. Is it sufficient protection (eliminating oxygen) to enclose them in my nitrile or latex gloves when I pull them off?

I don't want to burn the attached garage (workshop) and house down - my wife would be really upset!

[Howard Acheson]

The primary danger is with boiled linseed oil and products that contain boiled linseed oil or linseed oil with a dryer. These products would include an oil/varnish products like Watco or Minwax Tung Oil Finish, etc. ("Tung Oil Finishes" typically contain no real tung oil. They are linseed oil products.)

True, pure tung oil is not very dangerous. Nor is "raw" linseed oil very dangerous. Pure tung oil and raw linseed oil dry so slowly that they do not create any appreciable heat. If however, a chemical drying additive like "Japan Drier" is added to these products, the faster drying could cause enough heat for combustion to occur.

The best and safest way to handle any drying oil is to spread out the rags, or hang them on a clothes line. Let them fully dry and then they can be disposed of with your normal garbage.

[mike holden]

Doug,
There are commercial "flammables" containers, metal with metal lids, painted yellow or red with "flammable" on the sides. These are often available at going out of business auctions for little or nothing. These would be the best.
Second best is to get a metal, lidded container and fill half full of water. Put your rags in there and then burn them at your leisure.

I drape them over a metal trash can till they dry then put them in the trash.

Wadding them, and putting them into a glove is a recipe for a fire - DONT DO IT!

Mike

[Steve Vaughan]

...cause i had left a rag laying on my workbench (oak top) after apply BLO to a project. I left it for a while, a few hours, and came back to the house and noticed a STRONG odor of linseed oil. Since I'd just used it not long before, it wasn't 'too' unusual. Went downstairs to check on it and the rag was so hot I couldn't hold it! The benchtop was too hot to hold my hand on it!

I counted my blessings and never made that mistake again. I don't use BLO at all now, but Watco, and NEVER a rag balled up...always laid out away from stuff to dry. Lesson learned...almost the hard way!

[Howard Acheson]

>>>> but Watco

Not sure what you are saying here. Once the mineral spirit thinner in Watco evaporates, Watco is 85-90% boiled linseed oil. Probably more fires have been started by Watco rags than any other finishing product.

A balled up BLO rag and a balled up Watco rag are equally dangerous.

[Steve Vaughan]

Howard, understood... I was speaking more of the "never a rag balled up" part be it BLO or the Watco or just regular stain or anything else. Learned the hard way not to take those chances.

[Scott Holmes]

Howie,

Watco products are 75%+ mineral spirits not BLO. I think you may have just miss typed...

Still balling up the rags is a VERY BAD IDEA!

[Jamie Schmitz]

Most oils are dangerous. I have heard of finishing companies actually counting the rags before and after. The biggest NO-NO is to keep them in anything that won't let them out-gas. If you want to do an experiment put them in a closed ziplock baggie out in the sun in a safe place.
A water bucket is absolutely the safest way IMO.

[Howard Acheson]

>>> Watco products are 75%+ mineral spirits not BLO

Nope Scott, didn't miss-type. As I said, "ONCE THE MINERAL SPIRIT THINNER EVAPORATES", the material LEFT is 85-90% boiled linseed oil. The other 10-15% is a resin or varnish.