One of the things that confused me when I first started working in fused glass was which kiln wash to use. So far I have used both Hotline Hi-Fire and Hotline Primo primer. This is what I have discovered about them.
Application
The Hi-Fire primer, which has a pink color to it, goes on easier. It soaks into the shelf and dries almost instantly. That means no waiting between coats. The Primo primer, which is purple takes longer to dry and seems to puddle. Because of this I have to wait a bit between coats. The Primo primer also separates more and settles into a thick mud at the bottom of my jar. Each time I use it I have to make sure I get it mixed up really well before I use it. I just bought a wire whisk at the Dollar Store to help me mix it up. I had some marbles in the jar, but they just get stuck in the bottom.
Clean Up
Hi-Fire is a bit of a pain to clean off the shelf. I use a painter’s scraper to get the majority off and a green kitchen scouring pad to get the rest. Primo primer, as advertised, is easy to clean off. I just use the green kitchen scouring pad to rub off the old primer and follow with a damp paper towel to get the rest. In either case, I always wear a dust mask and rub gently to avoid sending the dust into the air.
Finish
Although both primers result in a smooth finish on the back of my pieces, the Primo primer was a bit smoother. To get the smoothest finish possible, I run the palm of my hand or a piece of rolled up pantyhose over the shelf before placing my pieces on it.
Conclusions
My conclusion is that each one has it place, and I will keep both in my studio. For my shelves, and molds I will mostly use the Hi-Fire primer. This primer will usually give me at least two firings on the shelf, and many, many, firings on the molds. Primo primer only gives me one firing. But because it is so easy to clean, I will use it for any molds that have more detail and also for castings. For example, my round pendants, like the one below, are made in a casting mold. In between firings I use a stiff toothbrush to clean off the old primer. I might also use Primo on the shelf if I am looking for an exceptionally smooth finish on the back. I still have to do some experimenting on which I prefer for high fire projects like screen melts. Primo ads say you can use it for firings up to 1550 degrees Fahrenheit. I couldn’t find any information on how high you can go with Hi-Fire.
Of course, I haven’t tried Bullseye’s primer yet. Would love to know what others are using and why. Please leave a comment and let me know.
Round Dichroic Fu…
I wanted to know if you cure the shelf after you apply either primer? I know the instructions on the hi fire say to cure it, but isn’t that just to dry the primer?
Wendy – The “curing” is just to remove all moisture. I usually prime two shelves at a time. One goes under my work bench and as long as it’s been several days before I use it I’m good to go. The other shelf I put in my kiln and fire afap to 250 F and hold for 5 minutes. That seems to be long enough to get the moisture out and still allow the shelf to cool in a reasonable amount of time so I can use it right away. I had an instructor once who didn’t even take the temp that high. His theory was that water boils at 100 degrees F so no need to go up to really high temperatures.
I only use the high-fire on my shelves. I don’t use the primo often; just in certain molds where it would be difficult to remove primer. But in either case you want the molds dry before using them.