Different glycols: any practical difference?

I'm interested in mixing Pyrocat-HD in glycol. Is there any practical difference between polyethylene glycol and propylene glycol?

john_s said:

I'm interested in mixing Pyrocat-HD in glycol. Is there any practical difference between polyethylene glycol and propylene glycol?

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Polyethylene glycol seems to be a lot more poisonous than propylene glycol.

argentic said:

Polyethylene glycol seems to be a lot more poisonous than propylene glycol.

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Yes, but the polyethylene tastes a lot better...

john_s said:

I'm interested in mixing Pyrocat-HD in glycol. Is there any practical difference between polyethylene glycol and propylene glycol?

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Sorry to pick nits here but I want to make sure you get the right stuff. The glycols you can use are ethylene glycol (used in conventional antifreeze) and propylene glycol. The latter is far less toxic than the former, and may actually dissolve typical photo ingredients more readily (i.e. at a lower temperature). This last bit is just a guess though.

The name "polyethylene glycol" (PEG for short) refers to a class of polymers that have molecular structures that makes them look like they are made from ethylene glycol (they aren't, in practice). The low molecular weight ones are thick oils and the higher molecular weight ones are waxy or soft solids. They are used in cosmetics, etc. They are not what you want for dissolving photographic chemicals (though they may work).

In short, propylene glycol = a good bet; ethylene glycol = it'll work but it's more toxic; polyethylene glycol = not suitable for this purpose.

You can also mix Pyrocat-HD in glycerine, which is very non-toxic, though its viscosity may be objectionable.

I have purchased both glycerine and propylene glycol in small amount (quart of less) from Artcraft Chemicals. For purchase of larger amount you might want to check out The ChemistryStore, at http://chemistrystore.com/

Sandy

PEG is used for food applications!
EthyleneGlycol can be poisonous if you drink it, prop glycol is less toxic.

For practical purposes there is little difference between them, except price probably and the risks involved.

argentic said:

Polyethylene glycol seems to be a lot more poisonous than propylene glycol.

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sanking said:

I have purchased both glycerine and propylene glycol in small amount (quart of less) from Artcraft Chemicals. For purchase of larger amount you might want to check out The ChemistryStore, at http://chemistrystore.com/

Sandy

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I buy propylene glycol in a shop for dairy cow farmers. Its 100 % pure form is used as a cow medicine against reduced milk production. About Euro 6,- / litre.