jon Anderson on mon 30 apr 12
Just got a sprayer from Harbor and I have a few questions, you can help
me expedite the learning process. First what are the pressure ranges
that you use for the gun. I presume by reading the directions that the
glaze will have to be thinned out , does it have to be thinned a lot or
just a little. Also with paint you just spray paint thinner to clean the
gun when your done. with glazes, can this be done with just spraying
water through it or will I have to break the gun down. I bought a gun
with stainless parts in it and a pressure gauge right on the gun, my air
source will be 100 feet away in my wood shop, so I'll be able to adjust
the pressure at the gun without having to run back and forth. Any other
Ideas , suggestions or anbything would be greatly apreciated.
Jon Anderson
jonandersonpottery.wordpress.com
Pottery by John on mon 30 apr 12
Hello Jon,
I don't have the Harbor Freight unit with the gauge, but it is similar to
what I have. I use 40 PSI as my go to setting, which seems to work for mos=
t
things. I also have (and recommend) their detail gun for highlighting areas
and will lower the pressure to keep an even coating. These guns come with =
a
plastic strainer in the connection from the container to the gun. Take tha=
t
out and throw it away. I was having all kinds of clogging issues until
Steven Hill told me to take out the strainer. I pour my glazes through a 6=
0
mesh strainer before I load and that seems to work well. The detail gun
seems to clog a bit more than the regular size gun. You can block the
discharge with a finger and get a little backpressure to unclog the gun for
minor clogging (saw Steven Hill doing that too.)
For cleaning, I dump any contents from the container back with the glaze
supply, then fill the container with water. I squeeze the trigger and the
water will gravity flow through the gun and you will see the glaze & water
coming out. Occasionally, dump the water and turn the gun over to let the
glaze & water backflush. Once the color in the flow through gets light, I
finish with spraying clear water through for maybe a quarter of the
container.
There are three adjustments on the gun. Since whoever made them didn't see=
m
to be able to write a manual, I found this guide a good source for how to
adjust my guns. http://www.luepottery.hwy.com.au/PDF/glaze%20spray.pdf
Again thanks to our Aussie compatriot, Des, for furnishing a link.
Good luck with your new toy,
John Lowes
Sandy Springs, Georgia
http://wynhillpottery.weebly.com/
Robert Harris on mon 30 apr 12
I use about 40 PSI. Really you want an HVLP (High Volume Low Pressure)
compressor, but if you have a large tank on a normal compressor it can
work. The biggest problem is running out of air really.
Personally I don't really thin out my glazes, but mine are probably
relatively thin anyway (1.35-1.6 g/ml). Incidentally, the problem is
viscosity not density, so quoting figures in g/ml doesn't really work.
I have a low viscosity glaze that I use at 1.55 g/ml, which is on the
high end of density for me, but is actually quite 'thin' in the
bucket.
The problem with high viscosity glazes are that they come out as blobs
and so you get a rough texture laid down by the sprayer. If your
glazes are glossy and fairly runny that doesn't matter, if they're
satin (or mat), then this texture will be apparent on the glazed pot.
Some people use this texturing to good effect.
Robert
On Mon, Apr 30, 2012 at 12:55 PM, jon Anderson wrote:
> Just got a sprayer from Harbor and I have a few questions, you can help
> me expedite the learning process. First what are the pressure ranges
> that you use for the gun. I presume by reading the directions that the
> glaze will have to be thinned out , does it have to be thinned a =3DA0lot=
o=3D
r
> just a little. Also with paint you just spray paint thinner to clean the
> gun when your done. with glazes, can this be done with just spraying
> water through it or will I have to break the gun down. I bought a gun
> with stainless parts in it and a pressure gauge right on the gun, my air
> source will be 100 feet away in my wood shop, =3DA0so I'll be able to adj=
us=3D
t
> the pressure at the gun without having to run back and forth. =3DA0Any ot=
he=3D
r
> Ideas , suggestions or anbything would be greatly apreciated.
>
> =3DA0 Jon Anderson
>
> =3DA0 jonandersonpottery.wordpress.com
--=3D20
----------------------------------------------------------
Vince Pitelka on mon 30 apr 12
Jon Anderson wrote:
"Just got a sprayer from Harbor and I have a few questions, you can help me
expedite the learning process. First what are the pressure ranges that you
use for the gun. I presume by reading the directions that the glaze will
have to be thinned out , does it have to be thinned a lot or just a little=
.
Also with paint you just spray paint thinner to clean the gun when your
done. with glazes, can this be done with just spraying water through it or
will I have to break the gun down. I bought a gun with stainless parts in i=
t
and a pressure gauge right on the gun, my air source will be 100 feet away
in my wood shop, so I'll be able to adjust the pressure at the gun without
having to run back and forth. Any other Ideas , suggestions or anbything
would be greatly appreciated."
Hi Jon -
Generally when you get a gun with a gauge on the handle, it is what is know=
n
as a "HVLP conversion gun." Unlike true HVLP guns, which run off a
high-volume-low-pressure turbine and cannot run off a normal compressor,
this kind of gun is designed to work on a normal compressor. If you are
really going to run 100 feet of air hose, then you want to jack the pressur=
e
up to 100 PSI or so at the regulator on the compressor. Generally on HVLP
conversion guns the gauge on the gun is set around 15 PSI while spraying,
but I have found wide discrepancy in this. In other words, I have seen som=
e
HVLP conversion guns that work great with the regulator at the gun set at 1=
0
PSI while spraying, and others that need to be set at 40 PSI while spraying=
,
which technically means that the latter really isn't HVLP. You will have t=
o
do some experimenting.
The glaze will only have to be thinned slightly. If it spatters or clogs
when you try to spray it, then it is likely too thick. Be sure to screen
the glaze when you pour it in the reservoir. Just a very fine-mesh kitchen
strainer or a 60-mesh glaze sieve works great. It will take out anything
that would cause problems.
You do not need to take the gun apart to clean it. Is yours a gravity feed
spray gun, with the reservoir on top of the gun? If so, there is a very
easy way to clean it. Just pour the leftover glaze back in the bucket (it
won't matter that it has been thinned slightly), rinse out the reservoir,
fill it with water, and screw on the lid with the little bleeder cap
removed. Hold the gun pointing downward in the sink with the spray nozzle
and the bleeder hole in the lid at the same level, pull the trigger, and
simply shake the gun back in forth in line with its length. This forces
water back and forth through the internal passages, and does a far better
job of cleaning out the internal passages in the gun than spraying clean
water through it under pressure.
If on the other hand you have the kind of gun with the reservoir below the
gun, then you will need to rinse out the reservoir and then fill it with
water and spray water through it, shaking the gun as you do so (to loosen
any settled glaze materials in the internal passages), until the water
sprays clean.
In case you don't already know this, one of the adjustment knobs controls
air spraying from small orifices in the "wings" of the nozzle assembly, and
this is what determines whether you have a round spray pattern or an oval
spray pattern. An oval spray pattern covers the surface more efficiently,
and when the "wings" are adjusted horizontally, the oval is vertical, and
that is what generally works best. Before you put any glaze in the gun,
hook it up to pressure and play with the knobs a little to figure out which
one controls the spray pattern. The knob that is at the back of the gun
directly in-line with the nozzle and needle controls the trigger travel, an=
d
normally you don't mess with that. That adjustment is used when painting
cars, but for spraying glazes you just want to have a lot of trigger travel=
.
When you pull the trigger, initially you get just air, and then as you pull
it further you get spray medium.
Hopefully you got a gun with at least a 1.5mm orifice, and preferably a 2mm
orifice. If not, then you should have asked us first. At the Craft Center
we are currently using a wonderful gun that is available on Amazon for very
cheap - around $40 - it is the Tool Force A-C1 50 PSI 2-in-1 HVLP Spray Gun=
.
It contains two needle/nozzle sets, and as soon as you get it you change
over to the larger needle/nozzle set and that is the one you use for all
ceramic media. If you didn't get that kind of gun, you might want to save
the one you have for painting cars and get the right gun for spraying
glazes.
The nozzle should be about eight to ten inches from the work, and you want
to see a visible wet spot on the surface of the work as you spray on the
glaze. If you hold it too close you will get a lot of running, and if you
hold it too far away the glaze will dry before it hits the surface and you
risk getting a fired surface that is like sandpaper. Having a little bit o=
f
running is less serious than spraying on inadequate glaze or letting the
glaze dry too much before hitting the surface. Don't move the spray gun to=
o
fast. Move as slowly as you need to in order to get a good wet spot
traveling across the surface of the work, but with little or no running.
If you have some scrap pots around, use them for practice. I have done a
lot of glaze spraying with every conceivable kind of sprayer, and I have
written about sprayguns and compressors in my Clay Times column, so feel
free to email me with questions.
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net
http://iweb.tntech.edu/wpitelka/
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