We recently bought a few new steel molds for the studio and needed to get them primed so that they'd be ready for fusing. Just in case you are new to fusing with steel molds, you will discover that kiln wash will NOT stick to a steel mold without heat and perhaps, as I have come to find out, a little luck as well!
Unfortunately we forgot how to get kiln wash to stick nicely to new steel molds, since we hadn't bought any new steel molds in a long time. A lot of glass artists use Boron Nitride spray on their molds but we already have Primo Primer on hand, so that is what we used. We didn't apply the shelf primer on the molds while in the oven. Instead we removed the molds (one at a time), painted, then put them back in the oven to heat up and also dry. A lot of glass artists put their molds in their kilns to heat up but our kiln is large and it is fairly inconvenient to heat them that way. We have also heard of other artists placing their steel molds on top of their kilns while they are running, but our kiln is very efficient and not enough heat escapes the lid to be able to heat the molds to an adequate temperature.
Above: New steel molds in the kitchen oven, heating up before applying kiln wash. We prefired the molds in our kiln to 500 degrees and cleaned them. We didn't use sand paper or Brillo pads on these but we see that a lot of glass artists suggest using them to rough up the surface allowing the primer to stick more easily.
Above: Kiln wash mixed in bucket with hake brush ready to use on the steel molds.
Above: Picture showing partially painted molds. The mold on the left wasn't hot enough to allow the primer to stick on the lower section.
As of today, I still haven't gotten my kiln wash (Primo Primer) to stick the way it should on the molds! I lowered the oven temperature to 200 degrees but that didn't help. I also used sand paper and roughed up the lower section of the smaller mold where the wash wouldn't stick at all but it still didn't work! Right now I've been working on these for three days, without luck!
As soon as I figure out what works for these molds, I'll update my post. Perhaps I'll buy some Boron Nitride spray after I try this a few more times.
So far some suggestions have been to use sand paper or a sand blaster to rough up the metal. Another is to heat mold in sections with a heat gun and apply primer. Another idea, mix my primer thicker. Also some say they spray it on with an airbrush (I don't have an airbrush). Others say wash it first with rubbing alcohol.
Ok so this afternoon I worked on the molds again. I washed and removed all the old kiln wash off the molds. I then used a little electric sander and sanded the surface area on the molds and once done I cleaned them with rubbing alcohol. I then set my oven to 225 degrees and put the molds in. I mixed up my primer so that it was fairly thin. Once a mold was heated, I removed it and then quickly painted on a very thin layer of primer with my hake brush. After that I put the mold back in the oven and set the timer for 5 minutes. When the timer buzzed after 5 minutes I put another thin coat of kiln wash on the mold and then put it back in the oven. I repeated these steps, with all molds until they appeared to have enough primer coating to work when fusing. Finally, it worked!
Above: Molds with kiln wash properly applied and now ready for fusing! The mold on the left is a floral former, the one on the right is a pendant light mold.