I have and use both, but they seem to be fairly interchangeable. Can I get away with just one of them? Are there any jobs you have come across where one works better than the other? The fact I am not keen on the smell of meths is a consideration too.
Difference between Isopropyl and Meths.
- Thread starter Rorschach
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DrPhill
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I used to be an organic chemist, so I can give you some information from the technical point of view, but I do not know how this translates to your practical concerns....
Chemically the two are very similar. Meths is actually ethyl alcohol (with added poison to stop folks drinking it). The molecules have a water-loving end (the alcohol bit) and a water hating end (the other bit of the name). The isopropyl end is slightly bigger and therefore slightly more water-hating than the ethyl bit, but this has little effect - the alcohol bit loves water so much that it overcomes the resistance.
Isopropyl alcohol will disolve greasy (water hating) stuff a little more easily than will ethyl alcohol. It will also dissolve in fatty tissues a little bit easier, and be harder for the body to remove.
The larger size (heavier weight) of the isopropyl molecule will make it less likely to evapourate - probably why it smells less. This also makes it slightly less of a fire risk.
Isopropyl alcohol is considered more toxic than ethyl alcohol.
Otherwise the differences are pretty small from a chemical point of view.
Chemically the two are very similar. Meths is actually ethyl alcohol (with added poison to stop folks drinking it). The molecules have a water-loving end (the alcohol bit) and a water hating end (the other bit of the name). The isopropyl end is slightly bigger and therefore slightly more water-hating than the ethyl bit, but this has little effect - the alcohol bit loves water so much that it overcomes the resistance.
Isopropyl alcohol will disolve greasy (water hating) stuff a little more easily than will ethyl alcohol. It will also dissolve in fatty tissues a little bit easier, and be harder for the body to remove.
The larger size (heavier weight) of the isopropyl molecule will make it less likely to evapourate - probably why it smells less. This also makes it slightly less of a fire risk.
Isopropyl alcohol is considered more toxic than ethyl alcohol.
Otherwise the differences are pretty small from a chemical point of view.
LancsRick
Established Member
Ipa doesn't leave a residue which is a major plus in cleaning applications if you need a truly clean surface. I think (don't know) I'm right in saying that meths will leave a residue which may or may not be a problem depending on your intentions.
Thanks for the info. My own research stated that meths is more toxic than IPA, not the ethyl component but the additives. Unless consumed, the IPA was considered the safest of the two.
I was mostly concerned with lack of de-greasing power and whether it was a suitable solvent for shellac etc.
I was mostly concerned with lack of de-greasing power and whether it was a suitable solvent for shellac etc.
Eric The Viking
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You're right about the additives to meths causing the problems. The methanol added is poisonous, but it's also got some colourant (used to be "methyl violet", IIRC, whatever that is), and I think like natural gas there's also a smelly additive (a mercaptan, possibly), to alert people and discourage drinking (methanol has little smell).
IPA was very popular in magnetic recording and film applications, because it would allow you to clean residues off magnetic heads (and from film gates, rollers, etc.), without dissolving the varnish holding head laminations together (originally - before epoxies, I guess). It was in widespread use in both the broadcast and computer industries for that purpose. Meths is also too volatile if used on a warm machine.
As an aside, I have a couple of bottles of meths from Toolstation that have gone completely clear now. I'm not sure why, but perhaps they no longer use methyl violet, but something affected by either sunlight or the plastic bottles used nowadays (PET coating?).
So from a practical perspective, meths will clean more aggressively, as long as you can keep the surface wetted. IPA is safer (WRT damage, not necessarily toxicity) but not as effextive.
IPA was very popular in magnetic recording and film applications, because it would allow you to clean residues off magnetic heads (and from film gates, rollers, etc.), without dissolving the varnish holding head laminations together (originally - before epoxies, I guess). It was in widespread use in both the broadcast and computer industries for that purpose. Meths is also too volatile if used on a warm machine.
As an aside, I have a couple of bottles of meths from Toolstation that have gone completely clear now. I'm not sure why, but perhaps they no longer use methyl violet, but something affected by either sunlight or the plastic bottles used nowadays (PET coating?).
So from a practical perspective, meths will clean more aggressively, as long as you can keep the surface wetted. IPA is safer (WRT damage, not necessarily toxicity) but not as effextive.
Very useful info here. Meths seems to be a lot cheaper too. I guess I will just keep both around and use the meths for rough cleaning, possibly finishing with a wipe of IPA to remove residue.
Regarding surgical spirit, if you read the ingredients you will see it has castor oil added to stop it drying the skin. I believe it is a blend of IPA, water and Castor oil.
Regarding surgical spirit, if you read the ingredients you will see it has castor oil added to stop it drying the skin. I believe it is a blend of IPA, water and Castor oil.
John Brown
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I'm going to have to stop drinking that Greene King IPA.
Phil Pascoe
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Rorschach":1qptmq8m said:
Not a lot, necessarily -
https://www.amazon.co.uk/LITRE-Grade-Is ... yl+alcohol
It's about £18 for 5ltrs from the same firm. It's useful to have have single litres, too - I usually pass a few on at a small profit.
Eric The Viking
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Ah, but that sort of IPA is used mostly for lubricationJohn Brown":he3ql55d said:
Phil Pascoe
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Rorschach":y7ik5f5c said:
Where? That would be about a quarter of the price. All the stuff I've come across is about £17 - £18 per 5 litres unless in larger quantities, and locally more than that.
novocaine
Established Member
I pay 80p for 1/2 litre in JTF for meths.
isopro tastes better than Meths and doesn't stain your teeth.
isopro tastes better than Meths and doesn't stain your teeth.
Phil Pascoe
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Anywhere near me it's £2.99 for 500ml.
novocaine
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to be honest it's been a while since I bought any, it could have shot up in price round here too.
I've got a stove that burns it but I haven't used it in a while.
I've got a stove that burns it but I haven't used it in a while.
Phil Pascoe
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Thanks. On my annual trip seven miles down the road to Falmouth I'll get someone to pick some up.Rorschach":2b35paxu said:
chaoticbob
Established Member
Meths has methylene violet and (when I were a lad) pyridine added to discourage consumption - also about 5% methanol to make you blind. The recipe may have changed though. But mostly ethanol.
It's surprisingly easy to get a licence to buy IDA (Industrial Denatured Alcohol) which is 99% ethanol (or rectified spirit perhaps) and 1% methanol - for our purposes indistinguishable from pure ethanol. I use this for making shellac based varnishes. I just filled in a form and said I wanted the stuff for making varnishes and the additives in meths were deleterious. Think I'm allowed 20 litres pa.
Ethanol is stronger solvent than isopropanol, and evaporates more quickly, which is good for for some things, bad for others. Depends what you're doing.
Rob.
It's surprisingly easy to get a licence to buy IDA (Industrial Denatured Alcohol) which is 99% ethanol (or rectified spirit perhaps) and 1% methanol - for our purposes indistinguishable from pure ethanol. I use this for making shellac based varnishes. I just filled in a form and said I wanted the stuff for making varnishes and the additives in meths were deleterious. Think I'm allowed 20 litres pa.
Ethanol is stronger solvent than isopropanol, and evaporates more quickly, which is good for for some things, bad for others. Depends what you're doing.
Rob.
