Strontium tests

When I work with strontium carbonate my results can differ quite a lot. The thickness of the glaze layer is very important for the color and the texture of the glaze. When I discussed this problem with a colleague ceramic teacher we did some tests with the same glaze. The difference was enormous: 

We tried to find out why. We used:

• same recipe

• same ingredients… (or? batch Strontium is possible different)

• same country (Belgium)

• different supplier

• different way of preparing the glaze 

• different way of applying the glaze 

• different size of kiln

• different firing/cooling schedule

I ordered different batches of Strontium Carbonate with different suppliers in Belgium and the Netherlands.  I made the glaze with water. The three batches need all a different amount of water to acquire the same viscosity.

The viscosity I aim for: the glaze flows of the rim of my plastic container in a slow but steady drip, like a creamy substance. Viscosity is not so easy to measure and the amount of my testing batch is not so much to fill a viscosity cup (Zahn cup). But with my experience of making glazes it was very obvious the three batches of glaze I made with the different Strontium Carbonates needs different amounts of water.  I need to add between 100% and 150% ! of water to the glaze to get a stir-able substance. Much more as the intermediate of 60% - 100% I am used to.

I made several tests with different water amounts and changed the viscosity with a drop of deflocculant (Dolapix PC67) and the glaze application changed a lot. Here you see the different results. Conclusion: the water amount is very important for the colour-result of this glaze and it can depend of the kind of (or batch of) material you use.  The use of deflocculant helps a lot to get a more stable result in the glazing.

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