MOTHER Feedback: Safety Regulations for Mexican Pottery and Combustible Gases

Eli P. Nielsen responds to two MOTHER EARTH NEWS NO. 31 articles about the need for safety regulations when using Mexican pottery and combustible gases.
By Eli P. Nielsen
March/April 1975
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Don't mistake my intentions: MOM and her children have the right idea. It's just that I want all earth people to survive their own efforts toward self-sufficiency. 
PHOTO: FOTOLIA/EMU


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Two "Dear Mother" letters in MOTHER EARTH NEWS NO. 31 prompt this city rat to write.

First, Bjo Trimble's advice on fixing lead glaze to make Mexican pottery "safe" for food handling kind of gives me the shakes. I'm no ceramic engineer, but I do know that most glazes — lead and non-lead — are actually thin layers of glass (or glasslike material, if you will). Such outer surfaces expand and contract at almost the same rate as the clay underneath and the almost is the part that gets you. Each time a vessel is heated and cooled, cracks form in the glaze. These are often microscopic and hence invisible but there can be miles (yes, literally 5,280 feet X ?) of such tiny fissures in one bean baker. This maze of cracks provides an enormous surface area that allows food acids to etch into the glaze and leach out the lead (cadmium, arsenic, etc . all good ceramics colors) into soluble toxic unplanned "food additives".

According to Bjo, the braceros taught her to bake the pottery in grease first, then boil it in vinegar. At the risk of sounding brutal, I wonder whether anybody has checked the average life span of braceros lately. It's miserably short and maybe mistaken "grandma" lore about lead-fired cookware causes as many deaths as short-handled hoes and pesticides.

A little knowledge of physics and chemistry suggests a possible modification of Bjo's process. First heat and cool your empty, dry bean pot rapidly several (6 to 10) times say by shifting it from a hot oven into cool, moving air and back. This ages and cracks the glaze without busting the pot. Then boil the crock with vinegar, but keep adding water so that the whole inside is treated. The acid will etch out all the fissures and remove the most soluble toxic salts. The next step is a further boiling with pure (distilled if possible) water — again with the vessel's entire surface covered — to remove more of the dangerous material. Finally, coat the pot's interior with corn oil, Crisco, or whatever. The grease, applied to a warm, dry, boiled-out pot, should soak into the cracks as if into a lamp wick. Since lead salts and the like don't dissolve in oil worth a darn, the resulting film acts as a barrier to keep food liquids (which are mostly water) from picking up too much contamination.

Warning: Don't bake in such ware treated or not. Cook in Pyrex or the like, and serve in the colorful, cute dishes if you must. Why? Because, if you heat the vessel long enough, more miles of cracks will open and expose more lead, etc. If you don't believe me, just ask any chemical engineer how to dissolve a solid. Somewhere in the course of his answer he'll tell you to "break the material up fine" — that's the cracks in the glaze and "apply heat in the presence of a solvent" in this case, the food cooking in that pretty, deadly pot.

I guess though I'm not sure that pottery treated as I've suggested and used for serving (not cooking) shouldn't pose too much of a toxicity hazard. Me, I'll stick to Pyrex!

My second worry is R.C. Nordvall's letter about his Philadelphia Globe and Light Company apparatus. This, I agree with MOTHER, could be an old acetylene generator or it could be one of another type that produced synthetic gas from partial combustion and/or quenching of hot coke or coal with steam. In either case, such a device and its product are no toys and must be handled with extreme care.

Acetylene is one of the touchiest gases around. Treated with proper respect, it's great but one slip and whoom! The list of safety regulations for an acetylene generator sounds like disaster will occur at noon unless every single rule is followed, and for a good reason: It will. Even a miner's lamp (a tiny, fist-sized mini-plant) can burn you severely if it blows. How big a bang, then, from a household fuel apparatus?

About the water gas/coal gas cycle generator: Its main product is carbon monoxide, a very deadly substance and also explosive in some concentrations. These properties are one reason why the gas company puts "odorants" into its product so you can smell a leak before it wipes you out.

Methane people, take heed also! One of the basic rules for any industrial (or back-to-the-land) toxic/flammable gas plant is: Don't ever guess about a generator which is already in operation. Study the subject enough to know before you start. Live MOTHER readers write good letters. Dead gas experimenters cause bureaucrats to pass ,new anti-do-your-thing laws. It's as simple as that. The "gasmen" — Ram Bux Singh, etc. — all mention safety. Please, MOTHER, yell about it!

For example: All the above-listed gas plants — acetylene, water gas/coal gas, and methane — must be purged before use. This is done by flushing and/or filling the whole system with inert gas (carbon dioxide or nitrogen), or by flooding it with water, to push out and exclude air because oxygen plus the gas being generated equals an explosive mixture. No instructions I've seen do more than "mention" this step as "important" and if nobody (or at least nobody who lived to tell about it) has had a generator blow yet, I can only say, "Wait a little while! It'll happen."

If I were writing directions for gas generation, the section on purging would read something like this: [1] Gas/air mixtures are high explosives. [2] The tiniest flame or spark from friction, static, etc., can detonate them. [3] The 1,000-gallon gas holder of a methane digester probably equals 10 to 50 pounds of good-grade dynamite in potential explosive power.

Therefore, when you purge your unit before starting or restarting it, observe the following rules: If you use carbon dioxide or nitrogen for the purpose, run at least 10 times the plant's internal volume of inert gas through the system (meanwhile testing for leaks, etc.). If you use a water purge — which is better — be sure every inch of tank and piping, right into the house or barn and up to the stove cocks, is full of water and not one tiny air bubble is left. Lots of work and mess? Yes, but you'll stay alive.

Carelessness with many of MOTHER's projects — wonderful as they are — can kill you. Don't mistake my intentions: MOM and her children have the right idea. It's just that I want all earth people to survive their own efforts toward self-sufficiency. Think before you do, dammit and do it safely or not at all!


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