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Whoa, this is scary stuff! Let’s check where this recommendation is coming from because I’m pretty certain someone has their percentages mixed up, with some scary consequences!!!
Ethanol is a) extremely flammable, b) a serious intoxicant and c) a strongly hygroscopic. What does all this mean?
First, 70% ethanol is A LOT of ethanol. Generally, when conservators use ethanol we use tiny amounts – fractions of 1% – to take advantage of the lower surface tension and to increase wetting of water-based solutions.
Hygroscopicity: At 70% ethanol will literally “suck” all the water out of any textile fiber causing extreme shrinkage, dessication that could be permanent. Almost all fibers have a latent “water of constitution” – water that is chemically attached to the fiber and fundamental to fiber properties such as strength, flexibility, drape and color. Loose that water by leaching it out with ethanol and there is no getting that water back into the fiber! Also, this reaction is exothermic – that is that heat is given off at the fiber as the water of constitution is lost. In the case of protein fibers, the temperature at the fiber level can exceed the temperature of shrinkage of the protein and the whole thing can collapse into gelatin!
70% ethanol is 140 proof alcohol. Inhaled, it will have you flat on your back in minutes and probably pretty nauseous, along with some upper respiratory damage. Secondly, it is a serious solvent for fats – This much ethanol will not only dissolve and extract the fats from your skin, it will do the same for your liver, eyes, etc. There are some NASTY health implications here!
ANY source of ignition – a static spark from your clothing, an on-off switch on the wall, a cell phone, a electric motor in a printer or computer, a water heater, an air conditioner – can ignite 70% ethanol into a MASSIVE ball of fire.
Does anyone know where this recommendation is written in the literature? Let’s get the numbers right!
Remember that at relative humidity below 62%, all conidia and spores (sexual and asexual “seeds” of mold) are inactive and the mold hyphae is dead. You do not have to KILL mold, you only have to dry it in conditions less than 60% Relative humidity. The pigmented staining caused by stressed mold is another story, altogether. But alcohol is NOT needed to kill mold. Mold conidia are ubiquitous in the air so there is no way to avoid it other than lower the RH.