Slip colours

[fionaSmith]

Complete newbie here  from Scotland.Interested in slip work.Is it possible to colour slip with paint ie acrylic or powder etc.I read to use oxide powder but I'm finding it extremely difficult to source a cheap solution as I want to firstly just experiment and try some slip decorating and to buy oxide powders in a variety of colours is very expensive and as I only need small amounts to experiment I wondered if paint or ink or paint powder etc can be used.

[Hulk]

Hi Fiona,

Welcome to the Forum!

For colours, there may be some choices that are less expensive?

If making up your own slip from clays*, red, brown/buff and white are common colors.

Underglazes provide a somewhat inexpensive way to get a lot of color; they don't go on the same way slips do, but they do have their uses...

Stains may provide a way to add a few colors to your slip palette.
The per pound prices I'm seeing are $12-18 (US dollars).

At ceramic temperatures, metals persist and provide coloring.
Blue/Cobalt is expensive (but it's come down a lot).
Green/Copper is more reasonable.

Maybe start with just a few colours?

Paints typically have some titanium dioxide powder, which provide most of the paints' covering/hiding ability, and perhaps some metal oxide(s) for color.
It's all the other stuff, a lot of which will burn away in the kiln, likely including some of the dies that provide color that I'd hesitate over.
The resultant smoke and fumes from burning paints/inks are enough to advise against; how the materials influence the slips' behaviors could be of concern as well.

*I blend bits of clay with water using a blender.
It takes a while, but it works to get a smooth consistency.
Then I run the slip through a sieve to remove sand/grog.
I sometimes use red slip to decorate white and brown ware.
I brush, dab, et cetera the slip on when the ware is still damp - right after trimming.
The moisture softens the ware - timing and care can be important!
After the ware dries some, carving is an option.

Hope that helps!

[Kelly in AK]

Haha! @Hulk you beat me to it! (What he said^)

Unfortunately most of those things designed for room temperature will completely burn away in the firing. Also, I’m not sure how helpful I can be, because I have no idea of the realities of buying ceramic supplies in Scotland. I can at least give you something to go on. Apologies if I’m giving you information you already know. 

As for oxides/carbonates, there are relatively few that are commonly used in studio pottery, Iron oxide being the most common, inexpensive, least toxic, and easily available. Copper carbonate, manganese dioxide, cobalt carbonate, tin oxide, and chrome oxide, are some others that come to mind. In other words, you won’t need to hunt down every metallic oxide known to man but if you do use oxides your color palette will be limited. That said, I would suggest most ceramic experimenters (probably most potters, to be honest) prefer using Mason stains for coloring both slip and glaze.

Mason is a brand name of ceramic stains and, while I have no interest in promoting them, they are reliable, used worldwide in industry and private studios. “What you see is what you get” after firing, which can’t be said for oxides. 

 

Edited July 12, 2023 by Kelly in AK

[Babs]

Also , you dont have to invent the wheel. Folk ha1ve been using coloured slip fir a long tIme. I suggest you tap in to other folks testings , select a range you like , remembering the colour of your clay body may have an effect and also your top temperature. Get a palette established for your pottery and then you may have to purchase just a few...to begin with.

All the best

[Min]

7 hours ago, Kelly in AK said:

Mason is a brand name of ceramic stains and, while I have no interest in promoting them, they are reliable, used worldwide in industry and private studios. “What you see is what you get” after firing, which can’t be said for oxides. 

 

In regards to the "What you see is what you get" with stains I have to respectfully disagree. For example if you put a chrome tin red stain in a slip it won't turn out red (even in huge amounts) because those chome tin pink or red or purple stains need low alumina plus quite high calcium to work.  Since slips are naturally high in alumina you are going to loose the colour. Matching the requirements of the stain to the slip or glaze can make a big difference in how the colours turn out. Many stains are not fussy about what the chem of the slip or glaze etc is but there are some picky ones.

[Callie Beller Diesel]

It’s also helpful to remember that whether you’re using stains or oxides, you’re only adding around 10% or less by dry weight to a given recipe. So if you’re only mixing up a 1 kg (dry materials) batch of slip, you’re adding 100g or less of the given oxide. With powerful colourants like cobalt oxide, 10g or .1% in that one kilo is enough to get a very solid colour. The 10% number would be for some of the lighter coloured stains. Many of the darker blues, greens, black, etc I’d start at 3-5% and see if that gives you the intensity you want. 

[Kelly in AK]

@Min, definitely true and a very important point! What I said only applies in the most general sense. 

[glazenerd]

Anything organic will burn off, and at most leave ashen residue. Paints are pigments, which is not the same as stains. As mentioned, you can use metallic oxides: cobalt, copper, etc. A possible cheaper way (I stress possible) is to find powdered glazes that are dark blue, dark green, etc: some contain metallic oxides, and others stains. Ask your local dealer. Do not get too carried away pending how high you fire: powdered glazes also contain high levels of fluxes. Clay/slips can tolerate flux additions, but do not overdo it. Stains work best with porcelain (white firing), or other high white firing bodies. Iron bearing clays will change the intended color. 

Tom

[Babs]

Also there is a difference between glaze stains and body stains.

[rabbethouse]

@Hulk @Kelly in AK When looking at iron oxide wash recipes it appears a 1:1 ratio of IO to Gerstley Borate is recommended. Would this be the same for Copper Oxide, Nickel Oxide as well? How about Copper Carbonate. I'm trying to get a more green wash. Thanks

[Callie Beller Diesel]

Hi and welcome!

Gerstley borate is a great standalone brushing medium and would be added to iron to help make it more workable, and to dilute the amount of oxide you’re using. (Some oxide is good, too much can cause glazes to crawl over it.) I find iron mostly doesn’t need help fluxing, but other oxides may.

if you want a green wash, don’t use the nickel. It tends to go brown.  Copper carbonate benefits from some kind of flux with sodium in it to help turn it green. GB does have some sodium, but if you try it and find it isn’t enough, try mixing equal parts epk, copper carb and any Ferro frit you have to hand. 3110 would be ideal, but 3195, 3134 and 3124 would also work. The epk will help make this mix brushable and dilute it, and the frit will do the flux/colour change part. 

 

[Kelly in AK]

What @Callie Beller Diesel said!

Copper carbonate would be my go to oxide/carbonate for greens, but chrome is green too. I don’t like it, but it’s definitely green. Teenage Mutant Ninja Turtle green is what comes to mind. Chrome is very refractory, plays differently than others. 

Ok, that’s out of my system. I haven’t real world tested these things enough to dispense much advice. As mentioned, iron works quite well without extra flux but will make glazes crawl if applied too thick (chrome does the crawling thing even worse). I mix 2% Veegum with iron oxide to keep it in suspension, water “to taste,” so it applies right. A lot gets wiped away with a sponge, to accentuate textures. Then again, I’m soda firing, so that’s like an external flux. Your results may vary. I can say copper goes from pale greens, to deep green, to black, to crusty black, quickly. It’s sensitive to thickness of application and affected strongly by fluxes. I wish I could be more definitive, but Callie nailed it closer than I can. 

[Min]

A tiny amount of chrome plus cobalt can make a really nice teal colour in washes, slips and glazes. 

@rabbethouse, have a look at June Perry's Wash Recipes, lots of good wash recipes. They are written for cone 10 but if you swap out the feldspar in a recipe for gerstley borate or Ferro frit 3134 or 3124 they should work at cone 6. For lowfire you would need to increase the amount of g.b. or frit.

 http://johnbrittpottery.blogspot.com/2013/03/june-perry-oxide-wash-list.html

[Pres]

Good selection of washes, but we should be aware that some of them will not play the same in Ox as they do in Redux. One in particular would be the Glick Purple Red or any Red that uses copper for the color red. In OX invariably they will be green.

 

 

best,

Pres