temperature for spraying lacquer
Mark Sauder
projects. I have some baseboard and trim that I want to spray
with lacquer. How low of a temperature can I spray lacquer
at?
Thanks.
Mark
Jack Lemley
I painted cars back when nitrocellulose lacquer was still used... I also use
lacquer on a lot of woodworking projects. I have sprayed at temperatures in
the 40s before but I don't recommend it... The finish will run easily.
Lacquer dries by solvent evaporation and that will occur at low
temperatures...If it is real cold spray lighter coats and allow overnight
dry time between coats...
Jack
All men die, but not all men truly live.. quote from Braveheart
Mark Sauder <m...@sgi.com> wrote in message
news:mfs-ya023580001...@news.corp.sgi.com...
Grumble
Accelerators and retarders are available and temps are on the sheets.
Warming the sprayroom for an hour or two first can help.
If you get it wrong the finish will not dry properly.
If you try to force dry the paint after application then it won't dry
properly because paint contains 2 solvents, one 'flashes off' quickly to
stop dust etc. sticking. As this solvent drys the 'skin' forms, the skin is
not 'airtight' and is designed to allow the second solvent (which hardens
the paint) to evaporate through it. When the second solvent has evaporated,
the paint is truly dry as opposed to touch dry. If you force it dry the
holes close up in the skin and prevent the second solvent evaporating, thus
keeping the paint soft forever.
Cheers
Bruce Rowen
65 F. Laquer dries by solvent evaporation and you can buy the laquer
thinner in various "speeds". The temp range for each speed is about
eight degrees so the idea is to determine your painting room temp
then buy a can of the proper thinner speed. Most Department store
thinner is a medium speed which is good for the mid 70's temp wise.
Note that all this applies to automotive work and may not be correct
for some primevil old growth oak.
-Bruce
Socorro, NM
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Bruce Rowen National Radio Astronomy Observatory
Scientific Programmer Array Operations Center
bro...@aoc.nrao.edu P.O. Box O Socorro, NM 87801
(505)835-7329 (505)835-7000
-------------------------------------------------------------------------------
jim mcnamara
It's the dry slowly part along with low temps that may cause problems.
The only good thing about cold spraying is that it's harder to get dry
spray. Everything else is not necessarily good.
You run into several problems. First, atomization lowers the temperature of
the lacquer/solvent brew as you spray it. Assuming the lacquer started at
ambient temperature, this will cause water vapor in the air to condense, go
along with the atomized spray, and then get deposited in the wet film.
This actually happens all the time when you spray - to some very small
degree. This is also why spraying at really high humidity is not
recommended - too easy to trap excessive moisture in the film.
The problem with cold spraying is that when you are down in the 30's & 40s
(F) the trapped liquid water (or ice crystals) stays suspended the film and
doesn't want to leave. It requires heat energy to leave - and there isn't
enough to get it to leave. The heat of transformation for water (energy
needed to get ice at 32F to change into water at 32F) is substantial, which
compounds the problem.
Anyway - minus all the science - the very likely result is a cloudy film -
blushing. Even if the humidity is on the low side when you spray, you may
still run into this problem. Normally, retarders will help get rid of
blushing down into the low 60s (F). A possible workaround is to heat the
workpiece with a lamp (wood holds heat pretty well), then spray. Or leave
the unfinished stuff inside in a warm place - then go inside, grab one,
spray it right away, go back inside, grab another, and so on. You had
better experiment on scrap first.
The other consideration is open time. Open time is the period of time when
the film is still wet throughout & soft. This has a couple of effects.
First, on vertical surfaces, sagging may occur as the film starts to flow
down. Normally the film's open time is about 10-15 minutes. At cold temps
this open time is extended to like one hour which gives the film a lot more
time to ooze down. Spraying really thin wet mils may solve this one.
Second problem is dust. One of the advantages of lacquer over varnish is
that lacquer dries dust free in 10 minutes. You are now letting it collect
dust for one hour.
I've communicated with one man on another board who says that he has
sprayed nc lacquer in the 30s(F) with no problem. My experience is just
the reverse. In fact, I ran some tests on it years ago for a furniture
company that wanted to save money on heating costs in a big finishing room.
My conclusion was that it was a no go below about 60(F)
You can check his comments in the archives at www.woodworking.org
If Chuck Ring happens to see this post, he can give you a direct URL to the
'cold' lacquer discussion. I hope. 'Cause I sure can't..
jim mcnamara
domingo rose
C.E. "Chuck" Ring
jim mcnamara wrote:
<snip of good material>
>
> If Chuck Ring happens to see this post, he can give you a direct URL to the
> 'cold' lacquer discussion. I hope. 'Cause I sure can't..
Rather than the direct URL which is longer than from here to Dallas,
here's the search engine for the archives:
http://209.122.88.33/InfoExchange/search.htm use "spraying lacquer" when
the returns come in click on "spraying lacquer sub zero" and the thread
will appear.
Chuck
Chuck
>
> jim mcnamara
> domingo rose
>
--
Gary Watts
: nc lacquer will spray alright and slowly dry at very cold temps.
: It's the dry slowly part along with low temps that may cause problems.
: The only good thing about cold spraying is that it's harder to get dry
: spray. Everything else is not necessarily good.
I agree with Jim that warmer temps are much more recommended. Faster
thinner helps although adding retarder to reduce blushing seems to be
counterproductive.
Gibson guitars has sprayed nitro lacquer for mulitple decades. It's
been noted that they use a hot plate with a double boiler to heat the
lacquer. I tried this recently and it works. Obviously, you want
to warm the lacquer, not boil it. DEFINITELY, don't use any open
flame method of heating!!!
Gary