Grey stain/ Glaze Not Turning Out

[Ceramic Human]

Having trouble getting some grey Mason Stains to turn out grey. I don't have a picture, but the pearl grey kept turning out purple and the sage grey turns out a lot more blue than we'd like. Included picture shows Sage grey at 4 parts to 100. Definitely not like the color showed. 

Firing to cone 5 and using Coyote clay's clear glaze as a base. Both  Glaze to stain ratios were 100grams -4 grams. Dipping once and holding for 3 seconds. Do I need to add a lot more stain or is it a firing or application problem? Any ideas?

 

Edit: Camera on phone was pretty bad but it is more blue than the photo shows.

[Callie Beller Diesel]

My first inclination is that it’s not the stain concentration, because 4% should be fine. My guess is that it’s probably one of the fluxes in the base glaze modifying the colour, but because we don’t have access to the recipe it’s hard to say exactly what. How confident do you feel with mixing you own base glaze?

[Min]

@Ceramic Human, you won't be able to find out what is in commercial glazes but should say if they are zinc free or not. What you can do though is see what is in the stains you are using. 

If you don't want a blue tint to the grey then avoid stains with cobalt as one of the ingredients. Sage grey is CrFeCoSnNi, so you can see it contains cobalt (Co) plus it contains chrome (Cr). So for this I would use a zinc free clear to avoid the chrome drifting to brown but it still could drift toward blue from the cobalt.  Pearl grey is CrFeCoAlSiNi, again it contains cobalt and chrome.

Many of the blended grey stains have been discontinued but you can still find them at some suppliers. Here is a link to Seattle Pottery Supply, it shows the chemical makeup of all the grey stains, look for one without cobalt to avoid blue undertones in your glaze and see if your local supplier has it and try a small amount of it.