Underglaze
48 underglazes / Speedball
All forty eight colors Speedball make. Underglaze is not glaze: it is the stuff you draw with, and it does not move or flow in the firing, which is exactly why it holds a line where a glaze would smear it.
Speedball reformulated the whole range in late 2023 for brushability, and list sgraffito, mishima, screen printing and detailed painting as what it is for.
Cone 05/6Bisque to Cone 04
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Underglaze by the numbers
48underglazes on our shelves
48at Purple Level
17carry an up-charge
Every Underglaze underglaze we have in house
Hover any tile to see a pot fired in it, or tap once on a phone.
Jump straight to one
Nothing by that name.
48 to choose from
How the Underglaze line works
Here is the rule that matters most, and it is ours rather than Speedball's. Underglaze goes on raw clay here, never on bisque, and every underglazed piece is bisque fired before any glaze touches it.
Speedball themselves allow greenware or bisque. We do not, and the pages here reflect how it works in this building.
Every tile on this page is half covered in clear glaze. The matte half is the bare underglaze, the glossy half is what you actually get on a finished pot.
Coats
Speedball ask for three liberal coats for full opacity. Fewer reads as a wash, which is a legitimate effect if you meant it.
Layering
Colors do not move or flow into each other during firing, so you can butt two right up against one another and keep the line. Speedball say they intermix freely if you want to make your own color.
Food and safety
Speedball rate all colors dinnerware safe when used and fired as directed, lead free, carrying the AP seal. On a functional pot they still need a clear glaze over them for a food surface.
Clays that suit Underglaze
On raw clay only, here. A light color over a darker body will need the full three coats, and White is the one to reach for underneath if you want a light color to stay light.
From The Clay Hole University
More info about Underglaze below, but first... Everything we teach about glazing, written down and taught properly. These are the glaze lessons, and they are a small corner of a library that runs from centering your first pot to selling your work.
UnderglazeHow to Use Underglaze: Techniques, Rules and Firing
UnderglazeMishima: How to Inlay Slip and Underglaze into Carved Lines
UnderglazeWipe-Away Texture: Underglaze and Oxide Washes on Bisque
GuideGlaze Brushing Techniques, Coat by Coat
GuideGlazing Big and Intricate Pottery Faster
GuideGetting the Most Out of the Mega Glaze Tool
GuideMaking, Logging and Dialing in Test Tiles
GuideGlaze Problems, Causes and Fixes
GuideGlazing on the Wheel for Even Coats and Clean Bands
GuideOxide and Carbonate Washes
GuideWhen to Use Celadon Glazes
GuideHow to Use Dipping Glazes
The Underglaze test tile pot
This family does not have a test tile pot. The colors and results come out close enough to what the book shows that a pot would not tell you much more, so work from the printed Glaze Bible and the tile above.
About these images and what your pot will actually look like
We have done our best to represent every glaze here accurately, and you should still expect your pot to look different from what is on this screen.
Our glaze tile images are digitally created. They are built to show the character of a glaze, not to be a color match.
A screen is not a printout, a printout is not a test tile, and a test tile is not a finished pot. Each step in that chain shifts what a glaze looks like, sometimes a lot.
On top of that, the pottery itself changes the result: the clay body, how thick the glaze went on, whether it was brushed, dipped or sprayed, what was layered under or over it, where the piece sat in the kiln, how hot that spot ran, how fast it cooled, what was fired next to it, and how much texture the surface had. Two pots glazed from the same jar on the same day can come out different.
Treat every image here as a starting point, and treat a test tile fired on your own clay as the real answer.