A couple of things tiny bubbles in enamels can be from,
First the addition of Klye-fire. I do my best not to use this but I realize in some designs we need it. The last time I used Klyre-fire, a mixture of 1-5 parts distilled water was best. It helps on a 3d surface but I could still see a few tiny bubbles. Klyre-Fire is very helpful on plique a jour. But you do see time bubbles.
Second way you can get those frustrating tiny Bubbles in enamels can be from sterling silver that has not been depleted properly. The more you fire the worse they get.*(
And last that I have seen, specks that usually come from old or deteriorating enamels. When you wash them you see tiny white specks in the container. On your first few firing you will see some are white in your enamel, then continue firing some look like beige-brown goo, and sometimes they turn into bubbles.
Patsy
I’m working with someone who does guilloche and I’m trying to achieve the best transparent colors to complement his work. I’m screening my colors with 200 mesh before washing and this has made a big difference, but I’m getting flaws in the initial flux coat. I’m using Soyer # (also screened at 200 mesh and washed) and firing at about 1500 degrees for 4 minutes. My success rate is about 50%. Sometimes there are little blotches of a whitish color and sometimes speckles and/or bubbles. Sometimes these flaws don’t show up until I do a second coat of counter-enamel. Any suggestions?
It is common to get bubbles in guilloche, the crevices in the metal are tiny and the enamel is not getting down into them. Try a finer grit, maybe 300 on the flux layer. But what metal are you working with? Sterling will start to bubble later in the enameling process or a cast peice if not depleted. 4 minutes is quite long for any firing. The only time I see blotches of white is if the enamels are bad. You can tell this if you wash them and let them sit for 30 minutes and they float in the surface of the water in the cup of the washed enamel.
Let me know if any of this helps. Patsy