Three words for three different places the colour ends up: under the glaze, inside it, or on top of it. They fire differently, wear differently, and they do not use the same toner.
Underglaze transfers
An underglaze transfer goes onto unglazed bisque. The piece is then glazed and fired, so the decoration ends up sealed under a layer of glass. Protection is total, but detail is not: as the glaze melts over the image, fine lines spread and photographic tone flattens. Traditional underglaze transfers are screen printed with underglaze colours, which is why they are sold as ready-made patterns rather than one-off photographs.
INEQS ceramic toner is not formulated for underglaze application to bisque. If a screen-printed underglaze pattern is what your work needs, a decal house with an underglaze range is the right supplier, not us. What most people describing an underglaze actually want, a permanent image that cannot wear off, is in-glaze decoration.
In-glaze decoration, which is what unfluxed toner does
Unfluxed INEQS toner is printed onto decal paper, transferred onto already-glazed ware and fired to between 860 and 1,150 °C. At that temperature the glaze softens and the ceramic pigment sinks into it. The image ends up inside the glass rather than on it: nothing to catch a fingernail on, dishwasher safe, UV stable outdoors, and as permanent as an underglaze, while still holding photographic detail and skin tones.
This is the route for tiles, porcelain, stoneware and tableware that can take a second high firing. See fluxed vs unfluxed toner for the full comparison.
Onglaze decoration, which is what fluxed toner does
Fluxed toner carries its own glass. It fires lower, roughly 805 to 900 °C, and the colour sits on top of the existing glaze in a thin layer of its own glass. That is what you use on porcelain that will not survive a high refire, on vitreous enamel, and on glass, where nothing above about 700 °C is possible at all.
Which one for which job
- Bisque you will glaze afterwards. Underglaze, screen printed. Not a laser process.
- Glazed ware that can take a high refire, and photographic images. In-glaze, unfluxed toner, 860 to 1,150 °C.
- Porcelain, enamel or glass at lower temperature. Onglaze, fluxed toner, 805 to 900 °C, or glass toner at 550 to 700 °C.
Why the words get mixed up
Search results run the three terms together because buyers describe the outcome, not the process. Somebody asking for an underglaze printer almost always means they want an image that will never rub off. In-glaze printing gives them that, with detail an underglaze cannot hold, and it works on ware that is already glazed rather than only on raw bisque.
Not sure which your ware can take? Send us the piece, the glaze and the kiln you have. We will tell you which route works, and say so if the answer is neither. You can also order test decals before committing to anything.