Monday, April 14, 2008

Solvents are not friendly

Derek Lowe is a blogger, and a pharmacological chemist, who spends a lot of his time doing chemical synthesis and analysis (as you would expect). Of course, in so doing, he spends a lot of time working with various solvents, and he's talking about them a bit today.

One of the solvents he calls out specifically, is methylene chloride (which is also called dimethyl chloride). As chlorinated solvents go, it's one of the most benign...

...which is kind of like saying "as gun shot wounds go, a .22 through the thigh is one of the most benign".

At least it doesn't kill you just from breathing it, or melt the skin off your bones; and yes, there are chlorinated solvents that will do just that. Some chemical warfare agents (like phosgene for example - in fact most chemical agents that are not organophosphates), and many pesticides, are just the gasseous or aerosolized forms of a chlorinated solvent (don't even get me started on flourinated compounds).

All the drama aside, it is a very useful chemical, and as I said, relatively benign.


Unfortunately, I have a lot of experience with methylene chloride.

My first real job as a teenager was as a furniture restorer and re-finisher in my uncles shop; and methylene chloride is (or at least was) one of the most common paint and varnish strippers for professional industrial use.

At any rate, it was what we used; because it is remarkably effective, and of the very effective strippers, it both works the fastest and is the least toxic.

I would spend several hours (sometimes as much as 16 hours a day) at a time standing in a large stainless steel tank, wearing a basic charcoal filter mask, standard cotton overalls (methylene chloride melts many synthetic fabrics; and you don't want to wear anything under the overalls that would soak up fluids and hold them against the skin) and chemical resistant gloves, apron, and boots; stripping furniture with a flow over system (essentially a hose pumping the solvent out through a scrub brush).

In order to strip these pieces, you have to get into every tiny little nook and cranny; and flow, brush, and scrape the crud off.

Now, most modern furniture is relatively clean, simple and square... but for the most part people don't pay professional restorers $75 an hour to strip and refinish those pieces. Mostly, the pieces they want done are 200 year old French provincial writing desks, and colonial post office desks, and 16 drawer armoires etc... etc...

Not simple shapes. Not square. Lots of fiddly bits and pieces, and hard to reach spaces. To get these things stripped, I would have to get most of my body fully into pieces of furniture that had this solvent all over it, splashing all over, etc...

We kept large amounts of mineral spirits and distilled water on hand, because methylene chloride burns like a sunofabitch on your skin, and it doesn't rinse off with water. You have to rinse it off and neutralize some of the burn with the mineral spirits first, then rinse that off with the water.

Several times a day I'd get large portions of my body covered by this stuff. On occasion, I would be completely doused from armpit to ankle; and in the course of these exceedingly painful soakings I discovered one of its secondary effects...

...It's a remarkably effective depilatory...

...and that's all I have to say about that.