I have not had previously had success with the glazed tiles. I tried to make a trivet but could only find a glazed tile in the larger tile sizes. I used craft inks and heat set it (350 degress for 20 minutes). It seemed fine but when I used the trivet for a hot dish and then wiped the spill off afterwards my design came off too. I will definitely have to try black Stazon and sharpies (I think the Stazon colors are ugly) on my remaining trivet that I have been storing for years!
However, I have had great success with unglazed tiles and craft inks by heat setting them. I have used them for hot things and wiped them off and the design stays on. I have tiles that I have used for years and they still look good.