Spraying glazes

[Kathy Ransom]

Does anyone have some advice for spraying glazes?  I use a small airbrush to spray underglazes and of course, have great luck with them going on smoothly.  I don't want to use my really good airbrush for my glazes though because I understand it is very hard on them due to the particle size, and of course I don't want to screen the glazes too finely because the particles give me the effects I'm looking for.  I'm using a larger automotive spray gun I bought at Canadian Tire but it constantly plugs on me and sometimes won't even start spraying.  I did brush my glazes on but really want a much smoother effect and I use a lot of different glazes in a small studio so don't have the space for more than a couple of them in big pails.

NOTE: Replies are posted from oldest to newest, so the most recent posts will be at the bottom of the last page.

[Kathy Ransom]

I had the same problem when I tried to use an hvlp spray gun as well but didn't have any more trouble when I went to a critter sprayer as long as I run clear water through it every 500 ml jar of glaze.

[robin campo]

the critter is a good choice for a good simple gun, the eze spray is similar and another gun which is even simpler is the Paasche 62 sprayer, it has nothing to adjust. The gravity feed guns are nice, but more complicated. I like them for larger coverage and the other guns for smaller pots or more precise control. Always sieve your glaze through at least a 40 mesh seive or so to get lumps out. If you use 50-50 water to dry in your glaze add 10-20% water to thin a bit or you may get more splatter or clogs. Underglaze is about all i spray through my airbrush and i thing it a little and sieve it also.

[George Lewter]

When you use a HVLP gravity-fed spray gun, settling of the glaze into the gun can be problematic, particularly if you have a manifold system and have several guns sitting around with different glazes, ready for use. There are several things you can to do to keep the glaze flowing.

• Each time you switch guns or pick one up after it has been unused for a few minutes, test and adjust the spray on the spray booth wall or a piece of cardboard before moving onto your pot. 
• If it doesn't spray correctly, hold you finger over the spray orifice and squeeze the trigger several times. This forces air back into the gun and bubbles it up into the glaze cup - in effect stirring the glaze, especially in the body of the gun where a clog will stop any glaze from passing. This also works very well when you are cleaning out your gun by spraying water through it (You can see the water in the cup clouding up with glaze from inside the body of the gun). Vary the finger pressure over the orifice until you get maximum bubble action in the glaze cup.
• Remember that you have three controls on your gun - a fluid control, an air control, and a pattern control for the shape of the spray (round to fan shaped). Use them, and you will be able to use different viscosities and get a variety of spray droplet sizes from fine mists to heavy splatters. 

It takes some practice but is well worth the effort.   

[Kathy Ransom]

Thanks George.  I started out with an HVLP gun but the settling caused a lot of problems.  When I discovered the Critter sprayer the settling problem was not such an issue but I still have my spray gun and will try your very simple solution (why didn't I think of that!)

[Ayjay]

I'm looking to start spraying glazes, I'd prefer to be able to dip but can't justify making the quantities which would allow this bearing in mind my small output, (pottery is a hobby for me).

Is there an optimum size for the nozzle on a gravity gun, is there a minimum size below which I shouldn't go?

For the size of compressor I have, a 1.00 mm nozzle gives me plenty of options for which gun to choose, larger is more difficult.

I sieve my glazes through a 100 mesh sieve if that's relevant.

[robin campo]

sieving your  glazes before spraying will cut down on splatter and you may need to thin your gaze a little. if you plan on glazing large work a regular size gun will work, for smaller work a touch up gun may be better, it is also lighter so less strain on your arm.

[Ayjay]

Thanks Robin; is there a nozzle size you would recommend?

[Dani Montoya]

I predominantly spray my glazes. I use a touch up gun with the largest tip that was designed for automotive use and I have had great success with it. Rarely clogs and I use commercial glazes, unstrained. The touch up gun I use is made by Sharpe and the tip is the 1.4 mm . You can see it here http://www.etoolcart.com/mgfhvlpminigravityfeedspraygun-1.aspx (Choose the 1.4 tip from the dropdown.

I have loved this little gun. It works way better than the big heavy guns. 

[Ayjay]

Thanks Dani, that's very helpful: that's quite similar to what I've ordered, (still waiting on arrival), mine has a 1.5  mm tip.

[Rodney Allen Roe]

Any advice on compressors?  What HP, pressure etc would be helpful.  I have a critter spray gun and nothing else. Thanks.

[Kathy Ransom]

I just use a fairly small shop compressor that I purchased on sale at Canadian Tire for about $50.  The air tank could be a bit bigger as the motor comes on quite a bit and is very noisy but it works really well with my critter sprayer.  I keep the pressure between 20 and 25 which gives me a good spray and adequate pressure to spray dust off my bisque which I do with the critter as well without the jar attached.  I like to keep things simple!

[Rodney Allen Roe]

I notice that Harbor Freight has a compressor air brush kit on sale.  I'm going to take a look at that.  Thanks Kathy for the advice.