Why Water should be treated as an ingredient in glaze composition.
One of the most important things in making glaze is the amount of water. No, not so much in purity but in the amount. We know that ceramic glaze is a suspension; Minerals floating in a suspension of water. When we apply glaze to bisque ware the water gets absorbed into the bisque body (which is a porous, open Network ) while the minerals that make the actual glaze stay behind as a coating on the pot itself. That is to say while water is the transport it is the minerals that directly make glaze when heated. Because one is floating / suspended in the other they both make contact with the pot at the same time. This presents a small problem. This means that technically a glaze has a ratio of water vs mineral, BUT! The amount of mineral doesn't change as per the recipe. This means the more water you have in a glaze the less mineral will be applied to the pot (with time being a variable of course) .
If I put 3 coats of a glaze on a pot that had 200 ml of water in a 100 g batch ( the average amount of glaze mineral in a recipe) I'm getting less mineral and subsequently glaze on my pot than if I put 3 coats of a glaze with 150 ml of water in that same 100g batch of glaze. TLDR: the higher the ratio of water in a glaze the less glaze mineral / glaze you are getting on your work when applied.
Take this experiment for example.
This is a picture of one of my oxidation red recipes called “ Ancient Greymon”. These are the same clay body, same kiln load, both dipped in the glaze for 3 seconds. Notice the one on the left has 200 ml written on the tile, That's right, One batch of this glaze (around 100 grams) has 200 ml of water. The tile on the left has a standard 150 ml of water in the glaze. The tile on the left, while treated and glazed the same way, has much more water in comparison to the minerals. Notice how much less mineral and color we get as a consequence. This is purely a result of the amount of mineral that coated the tile in comparison to the water it was suspended in. Usually potters would call this specific gravity but regardless of S.G you should always keep track of the mount of water in your glazes and recipes you make. Every glaze is different, there is no one amount of water one must put into all glazes. But if you want consistency it is best you treat water like an ingredient and start keeping the ml per 100g amount in your notes.
Doing this will eventually lead you to the concept of Specific gravity: the ratio of the density of a substance compared to the density of another substance (Usually water) . Its kind of like asking “What is the density of my minerals vs the water it’s floating in?” Which is a great question and honestly what you are doing. The tile on the right had a higher density of minerals int he glaze vs the water than the tile on the left. Which is why it received better color overall. This is a great place to start and a powerful tool in the fight for glaze consistency in your practice, and while it’s not the while story, keeping track of the water amount in your glazes is a prime first step.
P.S A horrid mistake in the glaze world is to write down a glaze recipe or try one from a book without paying attention to or writing down the amount of water that ought to be used in the glaze. If it is your own creation you can write down your preference and keep notes for consistency. But never give out a recipe without AT LEAST giving an amount of water that ought to be used for the recipe per batch. Any glaze book that does not have this metric is trash.
