This is a direct image transfer technique where underglaze is fused or “sintered” by the CO2 laser.
1. Apply a layer of underglaze to bisque
2. Etch an image - the laser selectively fuses the underglaze to the bisque
3. Lightly sponge off the unfused underglaze
4. Apply clear glaze if desired
Safety*
This is an experimental technique. Always consult a new material’s SDS (safety data sheet) before experimenting with it. Underglazes contain metal oxides and silica. Under any circumstances ensure there is adequate ventilation, but especially for experimental techniques - allow time for the laser to offgas and dust to be collected by your ventilation system. Consult with your makerspace/do your own research before testing this technique. Notes
Wax resist typically yields cleaner results than underglaze sintering. The advantage of the sintering technique is that it’s more forgiving of the laser being out of focus for slightly curved/round forms. Wax resist works best on completely flat slabs.Laser settings
90W laser
400mm/s
20% power
Left section - darker color, 20% power (more fusion)
Right section - lighter color, 15% power (less fusion)