What percentage of isopropyl alcohol works best

[daveyk]

I have to say, I prefer flux remover, but isopropyl alcohol is so much cheaper.  I have been buying 91% at Walmart's pharmacy for I dunno, maybe $2 a quart.

It works well, but not fast, on security sticker residue.

As for using it to remove flux residue, what percentage works best for you?  I was under the impression that the higher the better, but I was read somewhere that the water content is needed to help carry the dissolved flux. 

I will be picking up another bottle soon and am wondering what percentage most people here like to use, and if anyone knows for sure, what is the best percentage?

Dave

[SiliconWizard]

The problem I've found with isoprop alcohol is that with certain fluxes it leaves a very sticky residue that is hard to get rid of completely.

You could have a look at this discussion: https://www.eevblog.com/forum/suggestions/myth-busting-solder-flux-cleaning-with-isopropanol-alcohol/

[ataradov]

I see no practical difference between commonly available 91% and much more rare and expensive 99%. So I just go for the cheap 91% and it works fine for me.

[Ampera]

For general washing, a lower percentage might be useful, as the water does help move things around, while the alcohol helps dissolve parts of the flux. The issue with lower percentages is they can leave a residue behind, not sure if it's insulative or conductive, but it could be a bother for doing things like cleaning contacts.

In general, if you're wiping down something with a cloth, I'd just pick the 91%, as it's cheap, sold everywhere, and doesn't leave much of a residue.

[bd139]

90%+

You have to do multiple washes to get flux off with a brush at least. 3-4 usually does it for me.

[BBBbbb]

For cleaning surfaces from various residue (PCB/flux, optics) I'd say the higher the better, but if there is a significant price difference between 91% and 99% for flux/pcb 91% is OK.

Some general read, not too related:
https://blog.gotopac.com/2017/05/15/why-is-70-isopropyl-alcohol-ipa-a-better-disinfectant-than-99-isopropanol-and-what-is-ipa-used-for/

[Halcyon]

For sticker residue and other similar glues, I spray on a little citrus oil/ethanol solution (commonly sold as citrus air fresheners) on the gluey part, let it soak for 5-10 seconds then wipe away. Depending on the glue you might need a few applications, but once it's all unstuck, I finish up with a wipe of 100% Isopropanol just to get rid of any oily residue.

It's the best sticker/glue removal product I've found and it's safe to use on most surfaces. It's cheap, safe, fast acting and smells nice. I've used it on some pretty tough adhesives including 3M double-sided tapes.

The stuff I buy (linked in above) is 10-30% Limonene (from orange peel oil) with the rest being ethanol.

[MarkF]

For sticker residue (especially the store price stickers) , I use WD40 to remove the glue. Then, I use isopropyl alcohol to clean off the WD40.

[VK3DRB]

Any grade of isopropyl alcohol >90% is fine. The secret to clean boards is soaking them in the isopropyl alcohol overnight.

[sokoloff]

Immediately after you remove the seal on 99% IPA, it will start picking up humidity from the atmosphere anyway.
Last year's bottle of precious 99% IPA is probably under 98% anyway in any humid area.
Drugstore IPA works great.

[rdl]

I don't have any experience with rosin, but I spent 25 years formulating industrial finishes. A general rule is that for substances that are soluble in alcohol, ethanol is better than isopropanol. You can usually find "Kleen-Strip" brand denatured alcohol pretty easily if you want to try. The last time I checked, they had two flavors, regular and "Green". The "Green" version had much higher ethanol content, around 90%. The regular was more like a 50/50 blend of ethanol and methanol.

[raptor1956]

For general cleaning 30% is probably best, particularly when cleaning lenses and glasses etc.  There are things that 70% or 91% are better at, but if you really need a good solvent IPA may not be what you need.


Brian

[mbless]

Any grade of isopropyl alcohol >90% is fine. The secret to clean boards is soaking them in the isopropyl alcohol overnight.

Are there components that can't be left soaking in IPA overnight?

[bd139]

Timmers, polystyrene caps, humans.

[IanMacdonald]

Are there components that can't be left soaking in IPA overnight?

Anything rubber. May look OK when it comes out, but develop a case of obesity some days or weeks later.

[TheNewLab]

i buy my ISO alcohol and Walgreen's -99% never paid attention to the price difference. $2.50 vs. $1.00? $2.50 still better than $10 PCB washer.

Labels?
1st, diswashing liquid, soak and wipe,
2nd, iso alcohol,
3rd, Naptha -(lighter fluid)
This procedure works best for me, sometimes I can tell straight away what type of sticker, so which type of solvent.

I like the 50/50 solution mentioned above (methanol)!