This month I focused on creating a speckled glaze. My goal was to understand the difference between coarse red iron oxide and ilmenite in the way they form speckles.
Ilmenite is a mineral which contains iron and titanium. When used coarse and when not ground into the glaze or clay body, it will create speckles.
Coarse red iron oxide has a similar effect. When a glaze is not properly mixed, red iron oxide will create speckles, but in this case it was intentional.
The key to making a speckled glaze is to only the sieve the glaze before the speckles are added.
How the study was conducted
In this study, I tested adding quantities of coarse red iron oxide and ilmenite to a white glaze base.
I started by mixing 1000g of white dry ingredients and added them to 1000g of water. I then divided them into 9 containers of 200g each. This study only shows results from 3 buckets, but I intend to use the rest for other tests at a later date.
I used one of the buckets to test 3 speckle colors together at different amounts.
Click on the image below to see it larger.
Ilmenite produces speckles already at low quantity. The speckles look much more defined and "sit" on top of the glaze. See close up below, showing white with 2% ilmenite.
On the other hand, coarse red iron oxide produces speckles that are a lot more subtle and blend into the glaze. You can also see how, red iron oxide already alters the color of the glaze at lower amounts.
The photo below shows white with 2% coarse ROI and the one below shows white with 5% ilmenite.
5% ilmenite is a little too much speckles, although some interesting results can be obtained. See the same glaze on a bigger piece (porcelain).