Printing tiles

I think I have finally got the hang of printing tiles. It probably took me about 200 tiles to get the process to give good repeatable results. So I thought I would document the process for anyone else looking to do something similar.

Some of the results can be seen here:

cats, more cats, birds, QR codes

To sum it up in one line I use screen print technique with vinyl masks and under glaze in acrylic medium.

The process starts with underglaze powder which I get from bath potters and acrylic medium and screenprint medium. The media get mixed in equal parts by mass and then mixture is mixed in equal parts by mass with the underglaze powder.

(1 part acrylic medium : 1 part screenprint medium : 2 parts underglaze powder.)

Media before mixing

After everything is mixed

As you can see I mix it on a glass plate and ideally I would use a muller but I don’t have one, so a pallet knife must suffice for the time being. Once it is mixed, it needs to be passed through a screen to make sure it is lump free and won’t clog the printing screen. Some spreading back and forth with a pallet knife does the trick and i keep the storage pot underneath so that it can drop straight into it.

This results in smooth, lump free printing ink, which I store in a small self sealing plastic pot.

Now for the screen.

The “normal” way to produce a screen is photographically with emulations and washing and lots of faff. My method is to use a vinyl cutter (Silhouette Cameo) to cut a sticker that I sick to the screen. Much easier and great for short runs but it does limit the minimum feature to about 2mm square so no half-tone printing. Most of the time my work is silhouettes so there are a number of options for generating artwork. I tend to use my Samsung galaxy note or my Motion MC-F5 running Ubuntu and krita (A combo that makes a great graphics tablet for £100-ish). For QR codes there are plenty of web sites. In any case the idea is to get a black and white image of what is to be printed. In the software for the Cameo there is a handy trace function (based on Potrace for those that are interested) which then generates a cut path from the artwork. For things like the floppy disc tiles I am printing here I just found a photo of a floppy and drew the cut lines on the image in the software. Finally I draw a tile sizes square cut line around the design and flip everything before sending it to the machine to cut. The result:

To transfer this to the screen I use a low tack transfer paper:

peel off the backing and stick it to the screen, then remove the transfer paper:

finally, remove the bits I want the ink to come trough (in this case the grey window cover)

As the outline of the vinyl is the size of a tile this makes registering it on the tile quite easy. To make sure the tiles always remain in the same place I have some thin plywood “L”s that are taped to the base board. the screen also sits on one 1/4” thick ply spacers in the hinges to bring it to the correct hight for the tile:

(brown tape is just to stop leakage)

Brown parcel tape is used to mask off the rest of the screen and printing commences.

They go onto a ware board to dry for a bit then, where necessary, get the second colour and stamped on the back.

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Into a tile setter and then into the kiln (which I have put on wheels on a steel base so it can be loaded up next to where I am printing and wheeled off for firing) up to 960C in about 2 hours and then naturally cool

This fires on the underglaze and burns of the acrylic binder. Next glazing.

To glaze them, I use Duncan pure•brilliance™ Clear Dipping Glaze. I have decanted some into a plastic box and got the viscosity to 18secs by adding a little water. To mix the glaze I gently slosh it from side to side as violent shaking introduces air bubbles.  To do the dipping I made some dipping tongs from welding wire

Once all the bubbles and limps are dealt with using a small paint brush they go back in the setter for another firing 1060C for an hour

Result: