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Vic19/01/2021 15:54:14
2896 forum posts
8 photos

Anyone on here know the difference between 99.5% IDA (Ethanol?) and 99 or 100% Isopropyl Alcohol? Apart from the obvious .5% laugh

pgk pgk19/01/2021 16:07:06
2298 forum posts
293 photos

I believe the answer is that IPA is 'loosly' Propanol whereas IDA is Ethanol + some varant of nasty to make it unsuitable for drinking - usually methanol.
The difference being methanol CH3OH, ethanol C2H5Oh, propanol C3H8OH

So a bit like butane v propane - similar properties but more combustible carbon?


SillyOldDuffer19/01/2021 16:30:06
7487 forum posts
1658 photos

Same answer as pgk, except IDA is industrial meths, a mix of ethanol and 5% naptha. I think 99.5% IDA is industrial meths (95/5% mix) diluted with a dash of water, not 99.5% ethanol. It's controlled because Ethanol is a recreational drug only sold under licence with much tax added!

Isopropyl Alcohol is a different alcohol with unpleasant side effects.

IDA is cheap and is widely used as a fuel or unfussy solvent - where the naptha doesn't matter.

Propanol is mainly used when a pure alcohol is needed as a solvent for medical, cosmetics, ink and such. Meths works just as well except it stinks or spoils some things! Propanol is a good fuel but is rarely used because of the cost. (It can be added to petrol as an anti-knock agent.)


duncan webster19/01/2021 16:40:34
3466 forum posts
63 photos

IPA is no good for firing your Mamod, took me ages to get the soot off

Edited By duncan webster on 19/01/2021 16:41:14

Ady119/01/2021 16:41:50
4693 forum posts
713 photos

Once you add some irn bru there's no real difference

not done it yet19/01/2021 20:16:58
6285 forum posts
20 photos

IDA is normally denatured ethyl alcohol at about 95% pure - the rest being the denaturing chemical (often methyl alcohol plus a bittering agent - if appropriate) and water. The water is there because the ethanol is generally distilled and 95.5% is about the best one can manage by that means ( theoretical is 95.7%, IIRC).

Absolute ethanol is either produced by other means or chemically dried - hence is very expensive.

Michael Gilligan19/01/2021 20:34:06
18761 forum posts
922 photos

Realistically priced, high quality Isopropyl Alcohol is available here:


Well packed and promptly despatched too star


Robert Atkinson 219/01/2021 22:02:26
1076 forum posts
20 photos

IDA is Ethanol with at least 5% wood Naptha / Meatanol or simialr.

95% IDA is 95% IDA + 5% water i.e roughly 86% ethanol, 4% Wood Napha, 5% water.

99.5% has a small quantity of water, probably through absorbtion from the atmosphere (they can't prove it's 100%)

Note that in the UK you need authorisation from HMRC to buy or keep IDA. There is a 20l per year limit for members of the public for hobby use this still needs HMRC authorisation.

"Meths" is completly denatured alcohol - CDA no restriction on purchase in UK. It used to be dyed purple but that requirement was dropped in 2013.

Rober G8RPI.


Edited By Robert Atkinson 2 on 19/01/2021 22:04:47

Pete Rimmer19/01/2021 22:13:45
1053 forum posts
69 photos
Posted by Michael Gilligan on 19/01/2021 20:34:06:

Realistically priced, high quality Isopropyl Alcohol is available here:


Well packed and promptly despatched too star


No it ain't

This item is out of stock

Michael Gilligan19/01/2021 23:02:39
18761 forum posts
922 photos

I’m sure they will make some more soon, Pete

Actually ... I suspect they are about to revise the ebay price

[ it appears to fluctuate with demand ]




Edited By Michael Gilligan on 19/01/2021 23:03:43

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