Blue glaze projecting micro-droplets during firing

[Naton]

Hello,

I used a blue glaze for the first time. All the pieces projected micro-droplets of glaze around on the kilnshelf. Can someone explain me what happened? I fire at 1250 C  (cone 7).

[Dick White]

Cobalt does that in some glazes. I don't know why, just that it is a common problem.

[oldlady]

it happens.  someone familiar with the chemistry might explain it for you.   cobalt blue glazes seem to be the ones that do it.  this is why i am careful not to put cobalt blue pieces too near the edge of the shelf.  i don't want spots on the elements.   

 

[neilestrick]

Can you post the glaze recipe? Cobalt will fume and leave rings on the shelves, but if you're getting actual droplets of glaze on the shelf it may be from Gerstley borate spitting.

[Naton]

Hello! Thank you for your answer. Unfortunately , I don't have the recipe, this is a glaze I bought ( in powder). It's a terracolor glaze named Lugano. Firing range is 1200 to 1260 C. Could it be that it was too hot?

[RowanBloemhof]

I've actually used that glaze quite extensively myself. I too can remember it leaving this blue shadow on the kiln shelf where pieces were. It only did that when firing to higher temperatures. I usually fire it to 1220 C with better results. 

[Naton]

Thank you very much for this information.  The kiln was lightly loaded, I imagine the temperature was too high. I'll try at 1220 C.