Zinc oxide

[Babs]

Just flicking through old recipe book.

Can dense zinc oxide be substitued by zinc oxide?

Can't remember if i have any dense left in my shed.

[Callie Beller Diesel]

The only reference to density and zinc I could find was a brief mention on digitalfire about there being 2 different processes that can be used to derive zinc oxide, one of which creates a denser product. But the same article mentions that zinc oxide is one of the purest materials we deal with, so I would think that as long as the recipe is using weight and not volume measurements any substitutions would be chemically the same. 

That said, the density may affect other working properties. If the zinc is in the recipe as one flux among several it will matter less than if it’s something like a crystalline glaze.

[Babs]

Thanks Callie, not going for a crystalline glaze but having written that, the glazes I was reading through were matte.

[glazenerd]

Babs

Zinc is processed two ways: the French process and the American process. The American process is just simply “roasting” (we call it calcining) that removes impurities. It is denser because it typically 80% pure, with 20% of various minerals commonly associated with zinc. The French process involves vaporing zinc at higher temps, resulting in a purity above 99%. It is finer, with less density. The zinc you are looking for is called Maximo 910 in the States, unless it has been sold to another company yet again.

Tom

[PeterH]

Drifting off topic ...

I'm starting to get confused, because there are two ways of measuring the density of powders.

Bulk density is the weight of the powder divided by the volume it occupies (that's both the volume of the particles and any entrapped air).
Obviously this can be influenced how the powder is handled before the measurement.

Particle density is the weight of the powder divided by the volume of the particles. This volume can be measured by adding the powder to a liquid and observing change of volume. [The liquid must obviously wet the powder well.]

I'd always sort of assumed that heavy & light ZnO differed in bulk density rather than particle density.

Can anyone clarify things?

BTW references to light and heavy ZnO seem thin on the ground. But this supplier seems to be offering 98% pure heavy ZnO. Which suggests that "heavy" doesn't relate to density variations due to contamination with other elements (but may relate to the production process used.)  The listed "density" for this "heavy" ZnO is 5.606, wiki gives 5.6 for ZnO.
https://ie.vwr.com/store/product/787678/zinc-oxide-heavy-98

PS An earlier glazenerd posting describing the two processes in more detail.

 

Edited November 26, 2023 by PeterH

[Babs]

When I asked the question I was remembering a,lengthy posting on Zinc oxide. Fortunately? today I found I did have the dense zinc oxide in my supplies as well as a white powder. The dense Zinc Oxide was an off white, old supply.

Recipe I was going to try calls for

ZnO                     25

Pot Feldspar  40

Ball clay              5

Calcite                15

Silica 2oo           15

What does anyone think..desc nice domestic glaze with the addition of 4 part iron..olive honey colour.