This is a quick one. We found a marker in the school shop that doesn’t burn off completely, so is good for making tests at least so you know what you’ve done without having to worry that it might wash off. It doesn’t fire on at 650C, but it is totally stuck on a full fuse. Posca is the name of the company. Black burns out completely, silver mostly burns out, gold keps some colour but goes a warm grey, and all the other colours turn white, so it’s not useful for anything but white, but, that alone is kind of interesting. Also, while there are markers that burn off or can be washed off after they go through a full-fuse firing, and this is not one of them.