Isopropyl Alcohol - 70% or 91%?

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Hayabusa Rider

Admin Emeritus & Elite Member
Jan 26, 2000
50,879
4,265
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Originally posted by: kami333
Originally posted by: FelixDeKat
So Ive been a user of 91% Isopropyl (rubbing) Alcohol for various purposes for several years now and recently made the mistake of purchasing 70%. I had forgotten how weak this variety was and was disappointed when a strong aroma did not pierce of air when I opened the bottle. Furthermore, Im afraid that because it wont leave extremely dry skin behind that it is in fact not really "working". I have to see it to believe it! And I want to see the bodies of dead germs everywhere including collateral damage to supple skin surface.

Does it matter to you either way what type of alcohol you use? Or are you an indifferent middle of the road type, just going through life in a happy-go-lucky fashion not really caring if the job was done or not?

Actually 70% isopropyl is a better disinfectant. Alcohol works as a disinfectant by denaturing proteins, a small amount of water makes it more efficient.

Yep, it is.
 

ebaycj

Diamond Member
Mar 9, 2002
5,418
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Originally posted by: DanTMWTMP
Originally posted by: harobikes333
Originally posted by: DanTMWTMP
Originally posted by: Fayd
just got in the habit. too lazy to go to the store and buy aftershave, too forgetful to pick it up when i'm at the store. 1 bottle lasts forever.

yup, I use it as aftershave as well. I use it to clean the sink since it's the closest bottle of anything near my hand. That's why I go through a bottle very quickly. I use it to disinfect my toothbrush, the razor before I shave, as aftershave, to clean the buttocks area, balls and belly button (I found it it's the most effective way to get rid of and prevent the dank smelly-ness that happens down there).

... Dan do you by chance have a lot of free time? lol

You use it to disinfect your tooth brush and razor!? .... germ freak much?

eh i'm not trying to pick on ya fyi. just odd to me

:p I disinfect the toothbrush and razor because they seem to last longer when I do so. This is purely anecdotal evidence (my own perception), so take what I say w/ a grain of salt :p. I just mainly want to use my toothbrush for a longer period, instead of having to dispose of it and buy toothbrushes and razors more frequently.

If you actually store your razor with the blades submerged in alcohol, you will be absolutely shocked at how much longer they last. It's like 10x longer.

Use doesn't kill razor blades, rust kills razor blades. Submerging in alcohol right after rinsing = virtually no time for rust to form.
 

ebaycj

Diamond Member
Mar 9, 2002
5,418
0
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Originally posted by: Itchrelief
Originally posted by: DLeRium

Care to tell me the difference between IPA and Methanol?

One is a beer and the other makes you blind?

Methanol evaporates very quickly is all I know.

Ethanol = primary alcohol. grain alcohol, drinkable.

Methanol = primary alcohol. wood alcohol, leads to blindness if drunk.

Isopropyl = secondary alcohol. not drinkable.

 

RU482

Lifer
Apr 9, 2000
12,689
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70% for disinfecting (apparently the 30% water helps infiltrate the cells of the devious organisms, or so I've been told)
91% for cleaning and spraying in the eyes of strangers on the street
 

alkemyst

No Lifer
Feb 13, 2001
83,967
19
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depends on need, I have 70, 90ish and 99ish...I have acetone, mineral spirits, kerosine, etc in my workshop.

For isopropyl, 70% is great where 90%+ marrs the finish.
 

alkemyst

No Lifer
Feb 13, 2001
83,967
19
81
Originally posted by: thescreensavers
I get the highest amount I can get. You can dilute it as needed.

you can make it too.

For a buck I will get it in a concentration I know delivered via a bottle.
 

Auggie

Golden Member
Jul 18, 2003
1,379
0
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70% alcohol in the lab - from what I've been reading above, some people are misinformed about why 70% is better than high concentrations of alcohol. The 30% water (weight/volume) assists in reducing the evaporation time, so the alcohol is in contact with the surface for longer periods of time. Straight alcohol (most kinds) evaporate very quickly.

Hence why 70% for sterile lab technique, etc...
 

RadiclDreamer

Diamond Member
Aug 8, 2004
8,622
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Originally posted by: Leros
I've always used 91% for cleaning thermal compound off my CPUs. I don't use rubbing alcohol for medical reasons too much.

Arctic silver makes a TC removal liquid that works 100x better than alcohol. Give it a try.
 

Fayd

Diamond Member
Jun 28, 2001
7,971
2
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www.manwhoring.com
Originally posted by: RadiclDreamer
Originally posted by: Leros
I've always used 91% for cleaning thermal compound off my CPUs. I don't use rubbing alcohol for medical reasons too much.

Arctic silver makes a TC removal liquid that works 100x better than alcohol. Give it a try.

alcohol works well enough for me.
 
Feb 19, 2001
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Can you not get 99% anymore?

I went to Target to buy some on Saturday and all they had was 91 or 70. My 91% bottle is still half full at home, but my 99% is running low. I was hoping to get some 99%. Maybe Walgreens will have some more selection? After all my 2 bottles at home both say Walgreens on them....
 

zinfamous

No Lifer
Jul 12, 2006
110,511
29,096
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Originally posted by: catnap1972
Originally posted by: Xanis
real men use 91%

PSH--only wusses use anything but 100%

simply opening the bottle will invariably bring 100% down to ~97% or so b/c it will suck up whatever atmospheric moisture it can.

at least, that's what happens with EtOH.

 

FelixDeCat

Lifer
Aug 4, 2000
29,101
2,014
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Originally posted by: DLeRium
Can you not get 99% anymore?

I went to Target to buy some on Saturday and all they had was 91 or 70. My 91% bottle is still half full at home, but my 99% is running low. I was hoping to get some 99%. Maybe Walgreens will have some more selection? After all my 2 bottles at home both say Walgreens on them....

I havent seen 99 in years. About 10 to be exact. ;)

You may have to order online.
 

jagec

Lifer
Apr 30, 2004
24,442
6
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70% kills bacteria just as well as 91%, but doesn't work as well as flamethrower fuel in a Super Soaker.
 

alkemyst

No Lifer
Feb 13, 2001
83,967
19
81
Originally posted by: jagec
70% kills bacteria just as well as 91%, but doesn't work as well as flamethrower fuel in a Super Soaker.

QFT...I am not sure what others are using it for though....

I use mine for disinfection and as a solvent.

For most stickers 70% is good and will not mar most plastic.

For some 91-99% is needed but may mar/dull the finish if not careful. I know 90%+ will etch my mexican tile finish whereas 70% doesn't.

for stronger jobs I have acetone, mineral spirits, kerosene, xylene, denatured alcohol, etc.

 

alkemyst

No Lifer
Feb 13, 2001
83,967
19
81
Originally posted by: FelixDeKat
Originally posted by: DLeRium
Can you not get 99% anymore?

I went to Target to buy some on Saturday and all they had was 91 or 70. My 91% bottle is still half full at home, but my 99% is running low. I was hoping to get some 99%. Maybe Walgreens will have some more selection? After all my 2 bottles at home both say Walgreens on them....

I havent seen 99 in years. About 10 to be exact. ;)

You may have to order online.

Hobby shops and the like sometimes have 97 or 99
 

Parasitic

Diamond Member
Aug 17, 2002
4,001
2
0
In labs we used 70% ethanol for disinfecting surfaces, and that even works for mammalian cultures which are extremely susceptible to bacterial presence.
So yes, 91% IPA is overkill for biological applications unless you have something that needs drying fast.