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Spray Glazing Vs Dipping


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Hi everyone,

 

Hope you all have had a great weekend.

 

I'm a messy glazer with drips everywhere and have had to redo the process on more than one occasion. I've just had a wonderful result from spraying underglaze onto my work and I'd really like to have a perfect finish. 

 

My questions are:

 

Is it better to spray or to dip?

If spraying, how many coats do I give the ware?

 

Pics of the bisque below.

 

Thanks in advance for your thoughts 

 

Andrea

 

post-65376-0-69018300-1495985701_thumb.jpg

 

post-65376-0-33261200-1495985806_thumb.jpg

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you won't be able to get an answer to your question because nobody knows exactly how much underglaze you sprayed on your pots.  you won't know either until you see the finished results.  

 

sorry, you are embarking on an entirely new and entirely personal journey when you start spraying instead of dipping.  it is going to be a new skill and you will have exactly as much control over the results as anything else to do with pottery.  zero.

 

i have been spraying for several years now and still do not know until i open the kiln whether the pots have enough glaze on them.  the only advice anyone can give you is about the equipment itself.  we all work differently, my glaze is about as thick as a mcdonalds milkshake and i spray only a few inches away, marcia recommends thinner and she sprays from far away.  i spray greenware, she bisque fires first.  doc weathers has developed a thickness tool.  i wish that would work for me.  

 

sorry, no help.  but it does have several benefits for my work so i persevere.  

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Spraying takes more time and is slower-that said it offers more control. The whole trick is judging the thickness as Oldlady said above-you can scratch a needle tool thru dry glaze to see how thick on a test piece. The only way I know is do spray a lot -then you learn-learn by doing .

I spray on a banding wheel to spin the pot.

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If you are spraying over the overglaze, a starting point for thickness would be when you no longer see any color from those underglazes. But it is tricky. Other "rule of thumb" would be 1/32" measuring with a pin tool. Spraying a glaze on builds up in layers...fluffy layers unless you put it on too wet and it runs. then it is no longer fluffy and the 1/32" measure doesn't work.

 

Stephen Hill has been teaching layering effects from spraying for electric kiln ^6 firings. You may give him a look.

 

Dipping is quicker, but you may not get what to want with those underglazes. It depends on how well you handle dipping.

 

 

Marcia

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Thanks Marcia,

 

I found Stephen's article on spraying and it will help a lot. As oldlady says this is going to be a journey, but I think it will be well worth it. Having sprayed instead of brushing the underglaze I love the blended results and I can't see that dipping will enhance them.  As I said I don't do well with dipping. The little jug has been dipped, cleaned off, retried a number of times.

 

I'll post pics of the finished work.

 

Have a great week.

 

Andrea

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Spraying is all preference and practice. You can spray thick, thin or both. The results will vary depending on the glazes of course. I prefer to spray about 8-12 inches away. I also spray thin coat. I don't really enjoy a thick coat of glaze on anything. This is mostly because my work has a lot of surface to it and I want that to show through the glaze. If I was making straight sided/smooth shapes I wouldn't mind the glaze being thick as that would add a lot to the pot. Some of my favorite glaze work is a single glaze on a straight sided pot put on very thick. Think oilspots, snowflake crackle, celadon, etc..

 

As far as what is right, that is completely up to you and your work. There is no "correct" answer to anything. You can go as thin or as thick as you like as long as durability is considered.

 

One of the benefits of spraying is small amounts of glaze can cover huge pots. This isn't possible with dipping. The downsides of spraying if your going to be spraying glazes on thick is that it is slow, as Mark C said. It is really time consuming putting multiple coats on even an average size pot. This is the main reason I look to find glazes that do well sprayed thin. AKA matte/satin glazes. These glazes do very very well sprayed thin. 

 

Of course if your going to be spraying glazes your going to have to adjust your prices based on the amount of work your going to be putting in. Your product just became more time consuming to make and thus you either have to work harder or raise prices. If your not selling then this isn't a real concern. If you are, you should try to justify the spraying by making the pot more visually appealing as your application can be much more precise and interesting.

 

The best thing I can tell you from about 1.5 years of spraying experience is to carefully document how much you spray in the beginning. Number the pots and have a little book beside you when you spray. Count how many times you went around and the method you used, IE: feather, continuous, burst... Then needle tool the depth of the glaze if your doing it thick, and document it. After the firing your going to have a lot of good results and disappointing results. Find which ones you like, look back to your book of notes and try to repeat the process. One of the most frustrating things about spraying starting out is when you pull out a pot that you didn't put enough glaze. 

 

Also, find glazes that change colors or do interesting things when thick vs thin. These are your treasure glazes when spraying as you can mist a pot and get some beautiful surface.

 

Best of luck. Don't give up, it takes time and practice. I still pull out pots where I sprayed to much glaze or to little. It happens you get caught up in an idea or someone distracts you and boom. Woopsy.

 

Keep us posted.

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Andrea:

I spray tiles for production, and brush when just testing. I learned out of the gate to apply glaze on a per square inch(si) basis. The whole concept of dipping for 2-7 seconds is foreign to me. To me, it gives no useful data that I can use to calibrate application. To explain the square inch basis: a 12" platter would be 12 x 12 = 144 square inches. A light glaze application would be 0.15 grams per square inch, medium 0.25 grams, and heavy would be 0.40 grams per square inch.

An 144 square inch platter, with a heavy glaze would be: 144 x 0.40= 57.5 grams of glaze. You would mix it thinner and spray evenly. It will teach you quickly to apply glaze evenly, because you have an exact amount in the gun. You also have to learn how to adjust the air to material output of the gun. If the material output is too high: it will empty the cartridge too fast.

Lastly, mix plain ole silica with water and add 0.25% red iron oxide to give it a light rose color. Use this cheap solution to practice your spray technique. The light rose color will act as a tracer for you to use as a visual aid, so you can " see" how you are spraying. Like spraying paint, learn to use an arching fan pattern when you spray.

Nerd

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Just use EZ sprayer at 25 lbs pressure. Similar to the Critter.

 

Very low tech.

Marcia

 

Thanks Marcia,

 

I found Stephen's article on spraying and it will help a lot. As oldlady says this is going to be a journey, but I think it will be well worth it. Having sprayed instead of brushing the underglaze I love the blended results and I can't see that dipping will enhance them.  As I said I don't do well with dipping. The little jug has been dipped, cleaned off, retried a number of times.

 

I'll post pics of the finished work.

 

Have a great week.

 

Andrea

 

Be sure to keep us posted on your results and successes.

 

Marcia

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Just going to add a bit to what Tom wrote about the volumetric approach to determining how much glaze to spray.  Came across this pdf which uses the volume of glaze to area of pot method when I first started spray glazing. It's a long article but if you go down to around page 21 there are charts with bowl, platter, cylinders etc diameters with correlating square cm's. Makes it pretty fast to get the math about right. There are suggestions for volumes of glaze to use earlier on in the pdf plus quite a few little tricks and tips. It's more time consuming than just blasting the pot and guessing if you have enough glaze on but it gives you a good place to start. Once you've done a bunch of pots it's much easier to tell if you have the thickness about right at which point you probably won't need to do this and can guesstimate when the thickness is right by looking at it.

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Once you start spraying more pieces you will have a better idea of what coverage is needed. I use a turntable in a booth and I look for how long the glaze is taking to dry. This is how I determine how much glaze is applied and of course years of experience. Start out with some pots that you are not in love with just in case you do not get the results you where looking for. I prefer spraying larger work and for layering secondary and multiple glazes.

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[

Andrea:
I spray tiles for production, and brush when just testing. I learned out of the gate to apply glaze on a per square inch(si) basis. The whole concept of dipping for 2-7 seconds is foreign to me. To me, it gives no useful data that I can use to calibrate application. To explain the square inch basis: a 12" platter would be 12 x 12 = 144 square inches. A light glaze application would be 0.15 grams per square inch, medium 0.25 grams, and heavy would be 0.40 grams per square inch.
An 144 square inch platter, with a heavy glaze would be: 144 x 0.40= 57.5 grams of glaze. You would mix it thinner and spray evenly. It will teach you quickly to apply glaze evenly, because you have an exact amount in the gun. You also have to learn how to adjust the air to material output of the gun. If the material output is too high: it will empty the cartridge too fast.
Lastly, mix plain ole silica with water and add 0.25% red iron oxide to give it a light rose color. Use this cheap solution to practice your spray technique. The light rose color will act as a tracer for you to use as a visual aid, so you can " see" how you are spraying. Like spraying paint, learn to use an arching fan pattern when you spray.
Nerd

 

I don't get the grams per sq inch!  Could you please explain?  I wasn't able to spray the glaze due to a compressor malfunction -- HaHa and I ended up by dipping (see my post on pin holes) and ended up with only two small pieces with out any pin holes. I also had an electricity outage during the glaze fire.  Multiple issues in one fireing.  However the sprayed underglaze gave me some nice results.

 

attachment=8827:18767635_1851325515193512_8695764048092189375_n.jpg]

post-65376-0-58464700-1496283748_thumb.jpg

post-65376-0-31037900-1496284468_thumb.jpg

post-65376-0-75754300-1496283940_thumb.jpg

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AndreaB,

 

Use the link in Min's post. The measuring of glaze per piece is explained in the PDF. Also, at the end of the PDF is a table with sizes of pots and their area. It gives recommendations on how much glaze to use per 100 square centimeters. 

 

Example: 

bowl is 26 cm in diameter, so its
inside area is about 750 square centimetres. And the glaze
we’re using needs about 6 mL to 100 square centimetres,
so we need 7.5 x 6 = 45 mL approx Let’s use 50 mL
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Just going to add a bit to what Tom wrote about the volumetric approach to determining how much glaze to spray.  Came across this pdf which uses the volume of glaze to area of pot method when I first started spray glazing. It's a long article but if you go down to around page 21 there are charts with bowl, platter, cylinders etc diameters with correlating square cm's. Makes it pretty fast to get the math about right. There are suggestions for volumes of glaze to use earlier on in the pdf plus quite a few little tricks and tips. It's more time consuming than just blasting the pot and guessing if you have enough glaze on but it gives you a good place to start. Once you've done a bunch of pots it's much easier to tell if you have the thickness about right at which point you probably won't need to do this and can guesstimate when the thickness is right by looking at it.

 

Very interesting and useful article.  (Even if I'm never likely to spray.)  Thank you Min.

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