Silk screen over glaze

[Ktmountain studio]

I am interested in silkscreening over a colored glaze and was wondering what I should use as the medium. I was thinking engobe, but not sure if that would work. Also, would I have to do a third firing or could I do it all in the second firing?

[Callie Beller Diesel]

Hi and welcome!

Lots of potters use silkscrened images on pottery, and they typically come in two types: underglaze decals, and overglaze decals. Underglaze decals are usually ceramic pigments or underglazes printed on rice paper or blank newsprint, and are typically applied while the pot is still damp. Some of the commercial tissue transfers can be applied after bisque, but it's tricky to avoid making the image bleed. With underglaze decals, usually you then need to glaze over top with something transparent. Overglaze decals are also called waterslide decals, and they're screened or printed onto special paper and are applied to an already glazed surface and fired a third time. Some are printed with metallic lustres, some are printed with china paints, and these are fired somewhere around cone 018-016, depending on the manufacturer. There are some waterslide decals that can be fired to cone 6 as well, but they usually only come in black or blue.

The underglaze decals are the easiest ones to make at home as the screens and papers are pretty straightforward to come by. Some storebought underglazes are the right consistency to be printed with straight out of the bottle, although I imagine you could use anything that would pass through your silkscreen mesh size. 80 mesh is a common enough ceramic material size, but finer blends could be formulated with some effort.

[Ktmountain studio]

I was hoping to make my own screens, is there something I can use as an overglaze that isn't pre-made?

[Callie Beller Diesel]

I think I need a clearer idea of what you're trying to achieve. Are you thinking of doing something like Majolica style decorations, but with silk screened images?

[Ktmountain studio]

I am looking to do so something like this, but I want color (glaze) underneath, not just raw clay.

[Callie Beller Diesel]

There's two ways you could go about doing this.

The first, and likely easiest and cheapest, would be to screen print the image and add it like a tissue/newsprint transfer while the piece is wet, and add a coloured translucent glaze over it. 

If you must do it as an overglaze transfer, you'll need to look into screen printing china paints, and do a third lustre firing. This will be necessary if you're using it over an opaque glaze, although it will possibly involve a test or two to ensure your glaze doesn't do anything funky in the lustre firing. Some early melting glazes might give you trouble, although many will be fine. You could also send your images to one of several decal printers and have them made into waterslide decals if you need them in quantity, need them soon-ish or don't have the patience or facilities to do it yourself. If you really get into the process and want to make your own decals on a more commercial scale, a printer that will make black-only waterslide decals runs about $1000 US. Colour ones are $$$.

[neilestrick]

Underglaze and engobe are matte when fired, so maybe not the surface you want. Definitely not the surface you want if it comes into contact with food. There are products like Stroke-n-Coat that are glossy when fired, and could be done at low fire temps after glaze firing to cone 6. However, the cone 6 glaze may change when refired that hot, and you'll have a hard time getting the overglaze to stick to an already fired pot. Transfer decals are really the best way to apply something on top of an already fired  glaze.

[Min]

@Ktmountain studio, I think the mug could have been done using a cut out silkscreen plus Stroke & Coat thickened with Mayco silk screen medium. Could use it over a prefired glaze or bisque or greenware. I've used the Mayco silk screen medium, it did thicken up the underglaze I used it with. 

Like this:

 

[liambesaw]

Mayco silkscreen medium is just cmc gum if you already have that.  Just don't mix an entire bottle with it, because CMC gum rots.

[neilestrick]

2 hours ago, liambesaw said:

Mayco silkscreen medium is just cmc gum if you already have that.  Just don't mix an entire bottle with it, because CMC gum rots.

I would expect CMC to clump up quite badly if that's what it was.

[Roberta12]

Check out @elanpottery She does quite a bit with transfers.  Jason Bige Burnett does this also.  There are a number of ways to get color under your silkscreen.  Put UG on your leatherhard clay, let it dry to touch then go over it with the silk screen.  or put the silkscreen print on a Gelli pad and roll the cup over the print.  Check out ezscreens for video on this process. 

Roberta

[liambesaw]

1 hour ago, neilestrick said:

I would expect CMC to clump up quite badly if that's what it was.

Yeah, lots of people use different thickeners, that's just their product.  I use speedball screen printing transparent base ink if I need to, but speedball underglazes are nice and thick already.  I tried with CMC gum and amaco underglaze and it works, just goes bad after a few days.  Some people use corn syrup as well, but same rotting problem.

Maycos SDS states it's 100% sodium cmc, which is the non-food grade.

[neilestrick]

49 minutes ago, liambesaw said:

Yeah, lots of people use different thickeners, that's just their product.  I use speedball screen printing transparent base ink if I need to, but speedball underglazes are nice and thick already.  I tried with CMC gum and amaco underglaze and it works, just goes bad after a few days.  Some people use corn syrup as well, but same rotting problem.

Maycos SDS states it's 100% sodium cmc, which is the non-food grade.

A tiny bit of copper carb in gum solution will help to preserve it. When I make it, I use about 1/2 teaspoon copper to a gallon of solution, and it keeps forever. I make my solution 2 tablespoons CMC to a gallon of warm water, let it sit overnight since it clumps up and it somewhat hydrophobic when first added to water, then blend. If I'm making a brushing glaze from scratch, I substitute 1/3-1/2 of the water in the glaze with gum solution. The amount of copper in the glaze won't show.

[Ktmountain studio]

On 5/2/2020 at 11:05 AM, Min said:

@Ktmountain studio, I think the mug could have been done using a cut out silkscreen plus Stroke & Coat thickened with Mayco silk screen medium. Could use it over a prefired glaze or bisque or greenware. I've used the Mayco silk screen medium, it did thicken up the underglaze I used it with. 

Like this:

 

Thank you, this is what I was thinking of doing but just didn't know if I could do it over a glaze. 

[Min]

7 minutes ago, Ktmountain studio said:

this is what I was thinking of doing but just didn't know if I could do it over a glaze. 

Try a test and see, should work just fine. Just don't exceed the firing temp/cone of the original glaze.

[Smokey2]

On 5/2/2020 at 6:46 PM, liambesaw said:

I tried with CMC gum and amaco underglaze and it works, just goes bad after a few days

I mixed cornstarch into Amaco underglaze to make a thicker paste. Its getting close to 3 weeks and it's still good