What is Underglaze and How to Do It?
Underglazes are a great way to play with design, expression, and accents (or even transfers and printing like our Screen Printing on Clay Class!). It’s also hard to figure out which ones to use or purchase, as they can be pricey with confusing directions.
What is underglaze?
Underglaze is exactly what it sounds like! It goes under glaze, and can be painted on with precision (unlike glazes which can be unpredictable and runny). Underglazes are made of clay, water, and pigment. Underglaze usually looks pretty similar upon application and completion after glaze firing.
When to use underglaze:
Unlike slips,underglaze can go on greenware and bisqueware!
When applying underglaze on greenware, make sure it’s leather hard, first.
Pros of applying underglaze on greenware:
It won’t come off when you wipe the bottom of your pieces while glazing
You can try out Melissa Weiss’ technique of layering underglazes or carving
It’s easier to notice any spots you missed, as they’ll show up when bisqued
Cons of applying underglaze on greenware:
You might deform your piece if it’s too soft
It’ll take longer to dry, and you might leave finger prints
You can’t wash it off if you make a mistake (but you can paint over it)
When applying underglaze on bisqueware, it can be helpful to wipe your piece down with a sponge to help remove some of the dust.
Pros of applying underglaze on bisqueware:
You don’t have to worry about deforming your piece
If you mess up, you can just wipe it off and start over
The color will look clearer while applying
Cons of applying underglaze on bisqueware:
If you don’t wax over the bottom or anywhere that might get wiped, it can smear
You can’t do any fun carving
When does underglaze look best?
Underglaze will typically look the best in oxidation firings, as it can get muted in reduction firings. That being said, it can still look great in reduction! The glaze you pick can make a big difference, too. While clear glaze will often preserve the color the best, it can come out cloudy. Celadons and other translucent glazes are great ways to get all the color and add a fun tint!
We generally don’t recommend using underglaze in porcelain, soda, or wood fires, as the high temperature can cause them to burn off entirely. However, some colors, like black do great!
What underglaze to buy:
At GW, we primarily stock our studios with Amaco’s Velvet Underglazes or Speedball Underglazes, as both are reliable and fire well to cone 04 and cone 6! We prefer underglazes that are easy to paint on, well pigmented, and look good unglazed, as they are versatile and suit most needs of our students. However, there are a few types of underglaze (the ones linked below are all Amaco):
Spray On - Great for anytime you would use a spray and/or are looking lots of coverage
Liquid - Can quickly and easily cover large areas and work well for detailed work
Pans - These work like water colors; they are concentrated and use a wet brush
Crayons/Pencils - Just like they sound!
Most underglazes will give you specific cones to bisque to, but really, you can apply on greenware or any bisque cone (typically between 08 and 04). For glaze fire, cone 7 and under are always a safe bet, and higher fires can be okay. If you look up the type of underglaze, color, and brand, you should be able to find out if it can go to a higher fire without burning off. If you’re ever worried, make a test of your underglaze and glaze combinations! It can’t hurt :)
When buying underglaze, if it’s just for personal use, the pans or smaller containers are often a good idea. The bigger bottles can dry out before being used up, and can be frustrating to reconstitute (rehydrate to be made usable). It can also be helpful to transfer your underglazes into airtight containers with rubber gaskets and non-screw tops like these, as long as you can keep track of the colors and types. If you can, support your local art supplier or art thrift store (shout out Art Parts)! If not, the supplier usually sells directly.