Thanks, Jim, for your informative post on Borax and boric acid
firecoats and fluxes. I had always wondered about the chemistry
involved.
Your explanation makes me think of another question, though.
I routinely use the boric acid/alcohol firecoat on silver. Does it
have any use when working with copper or brass? I’ve been doing it
anyway, but can’t see that it makes much difference. It seems to
burn off pretty quickly. (I was hoping to avoid having to use the
hydrogen peroxide pickle on every last little brass piece to get rid
of the copper coating: it always seems to etch the surface too much,
then I have to sand again, etc., etc…Makes roller printing brass
seem pretty pointless.)
Another thing, of the petty annoyance variety: the alcohol in the
jar always evaporates too quickly. What are you all keeping this in?
A jelly jar with a rubber gasket is obviously not doing the job. I
wanted something with a wide mouth for dipping. The boric acid is
always a crust in the bottom, even when there is enough alcohol
left. It’s a bore to be always chopping it up and trying to make it
a solution again. Or am I just lazy?
Thanks
Lin Lahlum
Hi Lin. I know that crust all too well and have never succeeded in
getting it to go into solution after adding more alcohol even if I
have been able to reduce some of it to very fine particles. I presume
the effect is only physical but annoying, none the less.
On the other hand, when I add more alcohol at the point the solution
has become a thick slurry, all is well. Go figure! ?
I use unbreakable Lexan wide mouth jars designed for food storage -
they hold up about two or three years in my Arizona outdoor (patio)
soldering station. When they become crazed and brittle, I pick up
another at REI (Recreational Equipment Incorporated). I’m sure other
outdoor-type places probably carry Lexan jars but I didn’t find them
at our local Popular Outdoors stores.
As for the alcohol evaporation rate, it’s the nature of the beast.
One way to slow evaporation is to store in a container with a narrow
opening and a tight fitting lid - as alcohol is usually supplied. 
Since we prefer using wide mouth containers, we have to minimize
evaporation by slapping that lid back on our jar of boric acid and
alcohol as soon as we’ve dipped. That’s a good safety practice
anyway as it reduces the fire hazard as well as our exposure to the
fumes. Another suggestion is to set-up for two or three jobs (within
reason), dipping all the parts at once, and closing the container
before flaming off any alcohol remaining on the parts.
We are satisfied customers of REI but I cannot disclaim receiving
any benefit from them. We receive and use our REI member’s dividend
each year.
Pam Chott
Song of the Phoenix