Crystal glaze adjustments

[Potter3ee]

I found this recipe for a micro crystal glaze cone 6 on glazy and gave it a go. The first time I got gorgeous crystals and the second time nothing - just a super matt white glaze. Now the author of the glaze says that it is best used fresh - something to do with soda ash being soluble. The first time I used it right after I mixed it and the second time it sat for maybe 4-5 hours before I used it. Could that small amount of time be responsible for the crystals not forming? And my second question is, is there a substitute to soda ash that might work in the same way but produce a reliable glaze that can sit months without ‘going bad’?  Ive only just started mixing glazes so id appreciate any advice to troubleshoot this glaze. I really do love it and want to use this on the outside on my pots.

Nepheline Syenite 28.93

Spodumene 22.24

Silica 21.86

Zinc Oxide 14.14

Vansil W-30 Wollastonite 7.07

Soda Ash 4.35

Lithium Carbonate 1.4

[Min]

@tanvi504, for someone who is obviously interested in how glazes work it might be worth taking the time to start exploring the chemistry further. It's a huge help to understand the chemistry if you are interested in altering recipes like this. This is a fairly straightforward recipe to practice with, I'ld suggest giving it a try, see what you come up with.

Regarding subbing the soda ash in the glaze you posted, Ginger's Crystal Factory, click on the soda ash in the recipe on the Glazy page. It will take you to a page that describes soda ash. You can see that it supplies sodium. So now look up what materials we use that supply sodium that are more stable than soda ash. Ferro frit 3110 is one that I think of. Getting back to Glazy, try substituting Ferro 3110 for the soda ash and look at what happens to the chemistry. Keep adding Ferro 3110 until the sodium level is the same as in the original recipe. Look at the UMF (unity molecular formula) chart on the Glazy recipe page.  

Calcium amount will be slightly higher as the frit supplies some of that, drop what is suppling calcium (wollastonite) so the calcium is the same. Lastly, notice that the silica amount will have gone up since the frit supplies a fair bit of that too. To balance the recipe you would then lower the silica amount so the chemistry matches the original recipe. Finally re-total the recipe to 100 and you're done. At this point you could then test out the altered recipe and see how it does on actual pots.

[liambesaw]

Theres actually 4 soluble ingredients in there. Neph sy, spodumene, soda ash and lithium.  Very slightly zinc as well.

Though I doubt that was your issue here, it would take weeks for them to go into solution.

It looks thinner on your fully white one, and these crystals can grow into a matte very easily when slowly cooled.  So maybe it was cooled slower in the kiln than the test tiles

[neilestrick]

The soda ash is soluble, but it it dissolves immediately into the water so letting it sit around shouldn't change that. Over time the soda does not go away, however it can start to precipitate out and form crystals around the top edge of the bucket, but that would take a long time. The difference could be the thickness as Liam mentioned, but it could also be the amount of time you let the pot sit around and dry before it goes into the kiln. The slower it dries, the more the soluble soda will precipitate out to the surface of the glaze, and that can affect how it behaves in the melt. The crystals will also be affected by cooling rates, so if your kiln isn't as full, it will cool faster and you'll have less crystal development.

[Potter3ee]

@Min you’re absolutely right. Glaze chemistry is very intruiging to me and im so excited to explore further. Since its so new to me and the field is so vast and varied, it was nice to have a starting point which you have now provided. Thank you for explaining that. 
 

@liambesaw @neilestrick The kiln was fun on both occassions and it was cooled the same as before but I think you might be right about the thickness. The second batch was applied thinly than the test tiles so that might be the issue. Neil you mention that sitting out after being glazed can affect the melt. Did you mean letting it slowly dry outside would improve it or better to glaze and quickly fire it in the kiln?
 

 

[neilestrick]

4 hours ago, tanvi504 said:

Did you mean letting it slowly dry outside would improve it or better to glaze and quickly fire it in the kiln?
 

I have not idea which would be better, if either. But I think it's worth trying to both ways.