Strontium carbonate is the material most studios reach for when they want the matt surfaces barium gives without using barium. It is chemically similar enough to substitute in many recipes and different enough that the result is a relative rather than a copy.
Why it is used as a substitute
Strontium and barium behave similarly as high-temperature fluxes and both produce dry matt surfaces at the right percentages. Strontium is not regarded as carrying the same toxicity concerns, which makes it the more comfortable choice in a shared or teaching studio. Substitution is usually done by weight with adjustment on test tiles rather than by a fixed conversion.
How the surfaces differ
Strontium matts tend to be slightly glossier and less dry than the equivalent barium matt, and colours read a little differently, generally a touch less saturated. Whether that is a loss depends entirely on the glaze: for many recipes the strontium version is indistinguishable in use, and for a few specific barium blues it is not.
Using it in a glaze
It is added at similar percentages to barium and it fluxes strongly, so a substitution can change the melt as well as the surface. Test at the original percentage and then a little either side, on a tile with a vertical face so any change in fluidity shows before it appears on work.
Handling and cost
Standard powder precautions apply: ventilated space, fitted respirator, wet cleaning. It costs more per kilogram than barium in most catalogues, which is the practical trade for the easier handling, and the quantities used mean the difference on a bucket of glaze is small.
Questions people ask about strontium carbonate
Can I swap strontium for barium directly?
Usually by weight as a starting point, then adjusted on test tiles. It fluxes strongly, so the melt may change as well as the surface.
Is the matt the same?
Close but not identical. Strontium matts are usually slightly glossier and colours read a little less saturated.
Why use strontium at all?
It gives a similar matt without barium's toxicity concerns, which matters most in a shared or teaching studio.