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Re: gEDA-user: Isopropyl alcohol vs. ethanol

On 4/23/06, Karel Kulhavy <clock@xxxxxxxxxxxxx> wrote:
> Is it true that PCB's should be washed by isopropyl alcohol and not
> ethanol because ethanol has small molecules that creep into the part
> cases and wreak havoc there?

I've never personally heard this, but it is feasible I suppose. 
Ethanol is only C2H3OH, which is a much smaller molecule than
isopropanol.

In California supermarkets, isopropanol is vastly more popular (in
fact, you cannot even purchase a bottle of ethanol at most
supermarkets; the closest you get is Vodka), so I honestly cannot
remember a time when I actually possessed a bottle of actual ethanol.

> Is it OK to use denaturated ethanol (burning spirit) to clean PCB's?

Probably not, because the "denatured" part simply means infused with
*methanol*, which is an even smaller molecule yet.  BTW, methanol is
used specifically because it acts as a poison, thus hoping to deter
would-be drunkies from ingesting otherwise 200-proof alcohol.

> What's maximum safe time to leave a PCB inside the bath?

I always spot-wash individual solder joints.  I personally never bathe
a whole PCB.

> Is it allowed to pour isopropyl alcohol into the sink? Is the same
> allowed with denatured ethanol?

It depends on your locality, of course, but in the US, it is legal. 
Both are not only biodegradable, but also evaporate quickly (contrary
to popular belief, ethanol [at least] dissolves water, not the other
way around, so after it evaporates, all that's left is water).

You *probably* don't want to make a habit of it though, as I'm unaware
of any long-term environmental effects.  What follows is 100% pure
hypothesis.

Alcohol vapors in the sewer system may allow easier ignition of the
methane gas (it's like adding fuel additive to petrol), thus somewhat
increasing the hazard of explosion.  If vapors come into regular
contact with PVC or other plastic pipes, it may also contribute to
their dissolving, thus prematurely aging the pipe, or causing leaks.

--
Samuel A. Falvo II