[pianotech] Acetone vs. thinner

[Bob]

Hi Ed,

[It's my first try with the new list system, so I hope it works.] 
Anyway, I use acetone with hammer lacquer, for a lot of reasons. Apart 
from the fact that it dries faster, my understanding is that although it 
stinks, it is less ozone-depleting  and has lower toxicity than lacquer 
thinner(use ventilation and a carbon respirator anyway). Lacquer thinner 
has lots of solvents, which are useful for the control of flowout and 
drying speed when spraying, but not relevant to hammer hardening.

When under time pressure, I like to decide early on wholesale juicing, 
and do it right away. After ten or fifteen minutes, after the worst part 
of the nasties have flashed off, I blow on it gently with a heat gun. 
Don't try this at home, and don't sue me when the piano bursts into 
flames. You didn't hear it from me, disclaimer, disclaimer. Good sense 
is required; good general ventilation, don't get too close, keep it 
moving, don't char the hammers, keep feeling them to keep track of their 
temperature. Warm to the touch only. If anyone thinks I'm stupid for 
suggesting it, DON'T DO IT.

I've found that it dries on a rapidly declining curve; you can tell a 
whole lot about the direction of things in 30 to 45 minutes, more in an 
hour or two, only a little more as the day goes on. Especially if 
there's some touchup regulation to do, it can dry during that enough to 
do hammer mating/string leveling, then the tuning, then you can check 
again. Yes, it will continue to harden over the next day to week, but 
it's precious little, so if you aim for just a little under, it will 
probably be fine. Really, no voicing should be done in one shot, but if 
you're far away you might not have that luxury, and this probably gets 
you to the realm of touchup.

Ed is experienced with lacquer and has his own techniques, but for those 
who don't:
Depending upon the results I'm after, once the juice has done its 
initial wicking (within a few minutes), I often follow the general 
juicing with a brief squirt of pure acetone right on the crown, since I 
may not want it quite as stiff at the surface as I do right under. Then 
later in the day, a separate decision can be made right at the surface, 
since it dries even more quickly (especially with encouragement) than 
deeper does. If there isn't too much stuff in the hammer already, you 
can squirt the shoulders and watch it wick under the strike point and 
almost to the surface; otherwise you might need to go in right through 
the crown and follow it with straight acetone as above. Whatever you do 
almost always needs to include the part under the crown.

Let us know how it comes out.
Bob Davis



On 10/14/2011 10:54 AM, Ed Foote wrote:
> Ok,  somebody has some experience with this idea, 'cause I know it has 
> occurred to me in the past, but I didn't try it.
>     I may have to juice some hammers, tomorrow.  It is a three hour 
> drive from here, so I can't be around when the normal mix hardens. 
>  Has anybody gotten decent results with using acetone to thin the 
> lacquer instead of lacquer thinner?  Would it dry in a 5 or 6 hour 
> span if the hammers got a healthy dose?
>   Just wondering.....
> Thanks,
>
> Ed Foote RPT
> http://www.piano-tuners.org/edfoote/index.html

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