I had ordered some clear A4 stickers, yes A4, they are slightly sticky on one side, and rough on the other. You can if you wish use a fixative to stick them, but I don't think it is necessary, and it also just means more faffing. I had tried waterslide Decal paper, which did work, but needed treating with a fixative, an hour between each treatment! Next I tried some clear large labels, they were more like vellum, and while they were okay they were not quite what I wanted. Finally I found what I was looking for, these clear A4 sheets, they are not acetate, they come in a matt or glossy finish. I chose the glossy. They worked a treat on the candles for my nieces wedding, so I wondered if they would take a stamp... and yep, they do. I used a stayzon ink pad, I'm using small candles so need to stick to small stamps, but large stamps can be used on large candles. Printing on to them is easy peasy, no need for special settings, I just left my printer on the usual normal settings, though for a colour print go for 'best' or whatever your printer preference is for high quality. The sheets will also work for cards and scrapbooks, so that means the world is my oyster as far as printing my own sentiments goes.
I use alcohol inks on the candles, yes it sounds risky as the candles are going to be lit, but it is perfectly safe, I don't take the ink up to the wick, but leave a gap, I used masking tape (the usual type from hardware stores will do, you don't need the low tack stuff), once the ink has dried the candle can be burned normally. I know cos I've tried. The candles take the alcohol inks beautifully, it is best to just dab it on. I put the inks on the applicator, plus the mixer, and then dab away. You can put a couple of coats on if you wish. For this candle I used a mix of purple, silver metallic and pearl, it gave a nice soft finish. On some I've used a thin DST to add a thin strip of glitter, it is up to you. And you can use masks on the candles as well. Just experiment and have fun.
A happy crafting day.