Glaze Application: Spraying & Spray Guns

admin | Glaze Research, How-to & Studio Info | Sunday, September 30th, 2007

I prefer to spray my glazes. When done correctly, this method can create a smooth and very even coating of glaze. This way you don’t wind up looking at the piece after it is fired, wondering whether “that effect/defect” on one side is a result of a heavier or thinner application. Brushing and dipping can certainly be done with accuracy and has it’s own advantages, but spray glazing is still my preference.

When spraying, I place a piece on a banding wheel (I think Shimpo makes the best), and apply each glaze layer to the point where it stops drying… this will be just before it starts to run. I wait until the glaze sets up again (the watery sheen disappears) before spraying the next coat, so as not to distort the surface with the pressure coming out of the gun. But don’t let the layer dry completely, as you risk the first layer(s) bubbling/lifting up off the pot as it rehydrates. This “dry -but not too dry” rule applies to any application method, by the way.

Whether spraying, dipping, or brushing, I test the thickness of my glaze application with a push pin marked in millimeter increments (1-3mm) and record that in my notes. Many people use this method for testing glaze application thickness. The first time I read about this simple technique, was in the book “Ceramic Technology for Potter’s and Sculptor’s” (Cuff, 1996). John Tilton brought a depth gauge (sometimes incorrectly referred to as a micrometer), specially machined for testing glazes, to the Peter Ilsley Workshop in 2006.

HVLP Spray Gun

Concerning spray guns, I’ve had acceptable results with many types, but I think HVLP works best. I buy these from a place like Harbor Freight, my reason being that paint guns weren’t made to have abrasive glaze particles passing through them. In this regard, I’ve found that more expensive guns wear out just as fast under this type of (ab)use, so I buy the “cheapies” and treat them as disposable (actually, my most recent 3 have lasted over a year).

I also recommend gravity feed models… otherwise, you’ll have glaze left in the canister of the “bottom feeder” models, as they, well… don’t do all that good a job of feeding off the bottom… ;)

Incorporating additives such as suspension agents and binders to enhance the glaze’s storage and dry handling properties is a good idea. Click here for this info.

10 Comments »

  1. I want to spray large sculptural pcs. I have read your recommendations and it makes sense. what do you use for a compressor. I want to work with some Aamco glazes and thickness is important, where do you get the gadget to measure thickness.
    Thanks

    John Tilton modified a thickness gauge.
    I just use a fine metal file to mark a needle tool with mm increments.
    ~jesse.

    Comment by David Peterson — July 5, 2008 @ 4:36 pm

  2. Hi David,

    I use a 150psi compressor set outside of my studio (it’s loud). I also use two HVLP self contained “vortex-driven” units. The latter eliminates the need for a separate compressor.
    As for the “measuring tool”, I simply use a needle tool or a push pin that I file marks in at 1, 2, and 3mm increments.

    ~jesse.

    Comment by admin — July 13, 2008 @ 4:53 pm

  3. Hi Jesse, I looked on the Harbor freight website. I’m not sure which gun to buy. What model # do you use? My biggest fear is buying a gun that has a nozzle too small for glaze.
    Your website has been a great help.
    Thanks,
    Seth

    Hi Seth,
    I use model #’s 44677-1VGA & 46719-1VGA

    ~jesse.

    Comment by seth — December 22, 2008 @ 1:02 pm

  4. What output psi to you use to spray? Thank for all the information, I just starting spraying glazes with mixed results. Claire

    Comment by Claire — March 19, 2010 @ 5:34 am

  5. I am looking to buy a compressor and want to get by with some thing as cheep as I can. Home Depot is having a sale on small compressor, how big of one do I need for doing small pots and dishes ( the SCFM ratting is only at 2.5 )

    The larger the compressor, the less it will cycle on for re-filling with air (the things are loud!). I’d consider one of the all-in-one HVLP models from Harbor Freight. ~Jesse.

    Comment by Tom Blume — March 26, 2010 @ 8:43 am

  6. Thank you for taking the time and effort to share all this information. I was looking for information on spraying glazes and what kind of sprayer to buy, when I found your site. I’m on my way to Harbor Freight tools to get my sprayer! actually not “on my way” its late and I’ve had too much wine to drive right now, but soon I will be going.

    thanks!
    Brigitta

    Comment by Brigitta Dixon — June 2, 2010 @ 6:56 pm

  7. Do you know if there is any way you can get a spray gun to work or buy a spray gun that doesn’t require a compressor? I want to use it for glazing purposes and work in a shared studio space that I can’t leave equipment like that behind in.

    Many thanks
    Emma

    Emma,
    You could try the Chicago Electric Vortex Spray Gun Unit (it’s got a black and gray plastic housing with a 6-foot hose) from Harbor Freight. Kris Friedrich turned me on to these years ago. They’re easy to clean, absolutely portable, and I own two units which which still work great. The spray is adjustable, but these can really put on a lot of material in a short time, which is great for crystalline glazes. ~Jesse

    Comment by Emma — March 14, 2011 @ 5:52 pm

  8. Jesse,

    Thanks for the tips. i do have a few questions, as I just finished my first set of sprayed pots. I made a 1000 g. batch of crystalline glaze and managed only to glaze 3 pots of average size (max 8″ tall). Should I be getting much more out of the amount of glaze? I feel like half or even 2/3 of the glaze missed the friggen pots! Thanks_

    Justin Reese

    Justin,
    That is one problem with spraying unfortunately.

    Jesse

    Comment by Justin Reese — July 4, 2011 @ 12:44 pm

  9. I would like to spray my glaze on too. I have a 150 psi compressor It is a 6 gallon tank that says 3.5 SCFM at 90 PSI. Will that kind of compressor work with the spray guns you suggest from Harbor Freight?
    Thanks!!

    Hey Kathy
    I believe that will work.
    Jesse

    Comment by KATHY — May 4, 2012 @ 3:12 pm

  10. It should be obvious, but I want to caution a buyer of a compressor. Absolutely the air needs to be free of oil content. My wife uses an oilless compressor. If you know what you are buying you can add the right kind of filter to a compressor with oil bath, and you need to maintain it. It will need to be filtering for very fine particles. One could also install two in series, the first one for coarse and the second one for finest. One last point - never use WD40 or similar oil spray around the pottery, since its silicone oil will give you void spots on the applied glaze. Even the most minute deposit will mess you up.

    Comment by Dietrich — May 28, 2013 @ 8:54 am

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