I know a lot of people spray at skim milk consistency but I haven't found it necessary to have them that thin. With a HVLP spraygun and the compressor at 30 psi I have some that I spray that are a much thicker consistency than any dipping glaze I've ever used.
If I'm just spraying one glaze on a pot that doesn't need to be applied heavily then a thinner consistency is fine. When layering I tend to spray the glazes at a thicker consistency to avoid over wetting the pot. Just have to play with it until you get it sorted out.
Another question. If you refire to your glazes maturation point could this repair pinholes without affecting the look of the piece to much? I suppose it would depend on how runny a glaze is?
I hate pinholes, they turn up in all the wrong places don't they? Yup, refiring can smooth over pinholes but not always. You can rub a tiny bit of dry glaze into the pins and refire. I would put those pots in the coolest area of your kiln if possible. Yes, most glazes do move more on subsequent firings to similar cones. Sometimes they look better, sometimes not so much.
Couple other thoughts about pinholes if they are a real problem, apologies if you already know this stuff.
- clean bisque firing to around 05 - 04 with good ventilation, avoid stacking pots inside each other
- sub out any ingredients that have a high loi rate, for example if your glaze has a large amount of whiting it helps to reformulate glaze to use wollastonite in place of it (and some of the silica). Talc and dolomite have high loi rates also. Can't always get rid of them but helps if you can swap for something else like frit 3249 to supply the magnesium for example.
- glazes with high viscosity take longer to heal over the pins. Longer soak at the top temp without over firing sometimes helps.
I do a lot of testing, tweaking and from scratch glaze tests.
I use glaze calc program Insight (level 2 access). If a glaze looks good on paper then I'll run it through Insight, if it still looks good for the clay I'm using then I'll make a test batch. After that I tweak it with Insight to fix what isn't working and run more tests.
I'm not looking for crazing on my functional pots so I test for crazing. Usually make the base without colorants then if it passes my craze tests I'll try with colorants and or opacifiers, taking into consideration that some colorants and zircopax will help with crazing if necessary. I oven test for crazing by heating the test pieces at 320F for 20 mins then plunging them into room temp water, 3 cycles of this, then brush with sumi ink to check for crazing.
I use triaxial blends for both changing the base glaze and colour trials. I also like doing line blends.
I pay attention to silica and alumina levels as I make mostly domestic ware. I have sent a few samples for leach testing to Brandywine Labs.
I'm currently buying 2 claybodies and usually mix them together in the mixer/pugger. I like and dislike qualities of both of them and blending them seems to even them out.
Is there anything we don't test and mess around with? Seems I'm always trying out something new.