Hotline Primo Primer Sticking to glass – glass shattering

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    Hi, I have been fusing in a little Skutt kiln for 9 years – I have been using kiln wash I got somewhere and I don’t know what kind it is but I’ve never had any issues with it.I bought a new, very expensive kiln with a very expensive ceramic shelf and some Hotline Primo kiln wash. I washed the shelf 6 times and then heated it to 500 degrees and soaked for 20 min as the instructions suggested. Then I fired 3 pieces of glass – they all stuck to the shelf a little, 2 of them shattered. The one that did not shatter, the back is comepletely covered with the wash that pulled off the shelf and I cannot get it off. The back is very rough. The shelf shows exactly where my pieces were as there is no longer wash in those places. I never had this sort of issue with the old primer and would go back to it if I could remember what it was. I really am unhappy about this new primer – any suggestions? Or ideas what went wrong? I was using Spectrum glass 2 layers thick and my program was: ra300 to 1150 hold 30 ra200 to 1370 hold 20 ra400 to 1410 hold 12 ramp down quickly to 940 hold 60 ramp down 150 to 800 hold 30 min ramp down 150 to 0 Thanks – Penny

    Primo is a very fine kiln wash and settles quickly. It absolutely must be shaken or stirred every time a coat is added. If you didn’t do this you might as well have been brushing colored water on your shelf. Just a thought. Also remember that it is a 1 firing wash and should be reapplied after firing. Just brush off and reapply. I’ve used it for frit casting molds and have never had a problem.






    Hi Penny,

    Sorry to hear about your experience.

    I am not sure what is causing the problem…but have you contacted Hotline ( and asked them?  The only time I have had this happen to me was when I used a basic kiln wash that came with my kiln and fired opaque glass. Not that is keeps it from happening again, but you can soak your pieces in vinegar to remove the kiln wash and salvage what you can.

    I use Primo kiln wash and noticed that they have changed it. My experience with the new product is that is lasts longer on my shelves, especially when I do Paul’s kiln pressing. Before I would only get one firing per coating, now I have gotten at least 3 firings before I have to re-apply.

     I do apply my kiln wash by spraying.

    I just read the directions on the new container and it does mention “Mixed solution will precipitate to bottom of container. Shake vigorously.”  ….must be why they have now include the marbles in the pkg, -to make sure it gets mixed well. Did you stir the kiln wash well while using it?

    I know a lot of people use a garden sprayer to apply kiln wash…I have had very good results using the 99¢ spray bottles from Target. One of the sprayers last quite awhile.  I mix up the kiln wash in a jar with the marbles and when it is stirred well I transfer the mix to my spray bottle, including the marbles.  I shake/stir the sprayer very well before and during application.

    Hope this helps,


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