How do i know if I've applied enough kiln wash?

[CCVICKERS]

Hello!

I have a bunch of new molds that need to be kiln washed. With the exception of a classroom project and a frit ball project, I've only used MR-97 and thin fire paper so far. I didn't like the brush strokes I got on my classroom project, so I bought a gravity fed spray gun to apply the kiln wash. The kiln wash I'm using is what came with my Paragon kiln. I'm mixing the wash 5 water to 1 powder.

If I apply 5 coats with the sprayer, I can barely see the kiln wash. (I continuously shake the sprayer between strokes to make sure the powder stays suspended) On a couple of pieces I sprayed them until I had a consistant smooth white finish. This took about 10-12 passes. The surface on those pieces is powdery and I'm concerned that the powder will stick to the glass. I used the same wash mixture and applied 5 coats to one mold. The brush strokes look horrible and the wash gravitated to the inside angles of the mold. These particular molds are a light wheat color, not the white of a Bullseye mold.

How do I know when I've applied enough kiln wash? Should I see a solid coat or a translucent coat once it's dry?

Any advise on spraying kiln wash would be greatly appreciated!

Thanks,
Carla

[Stephen Richard]

The kiln wash is generically referred to as a separator. The fact that it is a powdery surface gives less possibility of sticking to the glass, unless you go above 720C.
I use Bullseye kiln wash that is tinted pink to give a contrast between a white mould or shelf and the separator. I coat my moulds and shelves with a sprayer too, and try to get an even pink appearance with little of the shelf or mould showing through. It is amazing how little is required to form a separation between the mould and the glass. I think Bullseye has a note on using kiln wash.

[Bert Weiss]

The answer is not simple or monolithic. It depends on what kind of glass you are firing and to what temperature. I get away with a much lighter coating of kilnwash when firing 10mm float glass to 1480 with a 12 minute hold, than people report their needs are firing Bullseye or Spectrum to the same temperatures. Slump temperatures are more forgiving than fuse temperatures. I sometimes fire float glass to above 1400 in a stainless steel slump mold. I want a better coating and a fresh coating when I do this.

That all said, if you see a coating of solid white after the wash has dried, it is probably good.

For the best sprayed on coating, I heat the mold to around 500, let it cool just a bit, and spray. If the mold is too hot, the spray will bounce off. If it is too cool, the wash will drip down. So, you want it to hit the mold, stick, and not run. With practice you can get good at this. You can always reheat when it cools down. The best angle is parallel between the spray nozzle and the side of the mold. Set up so you can walk around the mold, or rotate it.

[CCVICKERS]

Stephen, Bert,

Thank you for your response and education! I've ordered some Primo and Hotline Hi-temp to try. I believe they are both dyed products. I will practice with both.

[seachange]

hi

i add red food coloring to my kiln wash (spray it on shelves and molds). Brand is Queen, buy it in the supermarket (i live in Australia)

tried also natural cochineal food coloring, both work very well.

sometimes when i spray, if it looks a bit powdery, i rub it flat with my finger tips. this has to be done at the right moment, when it is not too wet, but also not completely dry

cheers, seachange

[CCVICKERS]

SeaChange,

Thanks for the tip! I'd thought about putting some sort of dye in the mix, but was afraid of an unexpected reaction that might stain the glass. Using food coloring completely escaped me!

I'm going to try this today!