How to color clay

by Marina Lespérance Lopez

color in clay: everything you need to know.

in this post i give all my tips and tricks so you can start exploring color in clay for yourself!

  • Where to buy?

  • Good health and safety habits

  • My essentials

  • How to make color charts and develop your own palette

  • How to colo clay

what are ceramics pigments?

Ceramic pigments are most often called ‘‘stains’’ in the industry. They are recipes formulated commercially by various companies including Mason, the industry leader today. Unlike the oxides which also can color clay, pigments are already fired so they are stable. The color you see in powder form is the color that will be more or less obtained in the end. (sometimes it will be lighter or darker, but there will be no transformation in color when fired. A blue pigment is most likely formulated with cobalt, but contrary to cobalt oxide which is lilac before fire and dark blue when fired, it is already blue when you get it. It is not recommended to play with oxides if you are not an well advised user: they are dangerous and very toxic. (as much in the powder state than when firing; they emane toxic vapors which can cause irreversible neurological damage.) Commercial pigments are produced with minerals (chromium, cobalt, cadmium, etc.) Which are fired and pulverized to powder. So the emanations already occured in a lab where needed protection and filtering equipments are available. Commercial pigments are generally "encapsulated", the toxic chemical element, cadmium for example, is "coated with a zirconium silicate crystal, which prevents the absorption of cadmium in the organism as well as protects the environment if waste is spilled. To learn more consult this article in depth on the subject.


where to get them?

  • Sial: Main supplier of the greater Montreal area, they have a good variety of stains but not all colors. You can however ask them to order colors that they do not have with Mason's reference number. The minimum quantity will be one pound for special orders, otherwise the pigments come in quarter pounds. (113 grams) Shipping fees start at 18$

  • PSH: Alternative supplier to Sial, located in Ontario. Could be interesting if you are not within the delivery scope of Sial. I do not find that their prices are advantageous: $ 16.25 versus $ 14 for the same red pigment # 6021. On the other hand, for another color, the Pink # 6020 is a little cheaper, $ 6.67 versus $ 7.25 at Sial. So check according to the colors you want which is most worth it. Shipping fees start at $ 12.50 for Quebec.

  • US Pigments: Us Pigments is an American company that has VERY favorable prices and sells only by the pound. Be carefull tho, the prices are displayed in USD so you have to do the maths to know if it is still a good deal. I hesitate to recommend this company despite their very competitive prices because I sometimes had problems with consistency: my tests do not come out the same from one time to another. For example, for a pound of red # 6021 it costs about 38 $CAN with the exchange rate, and at Sial 48 $CAN. So order at your own risk and will will never stress this enough: always re-test your recipes! Note that costumer services is are great even tho the consistency issues and I have received refunds for problematic batches.

  • The Sounding Stone: Canadian site, a company based in Manitoba which holds a wide variety of products for ceramists including several stains. The prices are not really competitive but it makes it possible to buy certain pigments in quarter pounds which are not available at Sial like the color Mango that I love for example that otherwise it would be necessary to order a whole pound that cost around 70 $.

health and safety precautions:

As always in a ceramic studio it is important to have impeccable hygiene to protect yourself from toxic matter; Wearing a mask in the presence of materials in their powder form, an adequate ventilation system when firing and if possible a programmable kiln that allows you to leave the premises during firing is even better. (ceramic materials give off vapors which can cause irreversible neurological damage during firing, and the first bisque firing is where most of the gases are evacuated. We would tend to think that the hotter the more dangerous it is but on the contrary, the first 1000 degrees are the most critical. Unlike dust, the vapors given off by the filn are imperceptible, so it is more difficult to protect yourself.)

In terms of skin contact, pigments are (in theory) safe; consult the technical sheets of the companies for the precautions to take for each pigment: The technical sheets generally prescribe wearing a particulate mask but "that the use of glove is not necessary for normal use" To me, “normal use” is very vague, we do not know not what it would be considered excessive use, it is not stated in the safety data sheets. I did researches and I can't seem to find more information on the subject. Some ceramists work with gloves and others do not, there is no consensus on the subject.

  • Please consult the SATEFY DATA SHEETS before using stains.

  • Be meticulous and organized when handling the pigments: work them wet as much as possible and otherwise wear a mask.

  • Keep tools and work surfaces clean, wash after all uses.

  • Keep hands clean and skin hydrated, make sure your skin is free of lesions before handling. When in doubt wear gloves.

  • Do not keep your workshop clothes at home and take a shower after a day of workshop. There is dust on your skin and in your hair and you could contaminate your environment. (For my part, I will never go to bed without taking a shower after a day of work, even if I finish at midnight and I am very tired, it is non-negotiable)

my go tos:

There are above 90 shades available from the Mason company in addition to all the other brands., and the colors represented on the sites are often not very representative of the results that can be obtained so it is very difficult to get around. Some pigments do not show up in coloring in body staining and require special glazes to develop the color. (Pay special attention to all the pinks, most won’t show up!) For my part, I have some essentials and each time I buy them I take one or two more new ones to try them out. I'm starting to have a good collection of swatches. To get starting I suggest these; which are my go tos. With this base you can make a range of different shades by mixing them together.

  • Black: 6600 Best Black

  • Blue: 6388 Mazerine (primary blue)

  • Greens: 6242 Bermuda (light turquoise) ET 6254 Dark Teal Green (dark teal green)

  • Violet: 6304 Violet Chrome Tin (lilac)

  • Red: 6021 Dark Red (primary red)

  • Orange: 6028 Orange (primary orange) (bonus: 6030 Mango is a very beautiful orange-red giving pretty corals in dilution)

  • Yellow: 6450 Praseodymium (very bright yellow like CYMK yellow)

    (Optional)

  • Gray: 6503 Taupe (mouse gray) (You can avoid buying a gray by diluting the concentration of black.)

  • Brown: 6160 Dark Chocolate (dark brown)

    (There are so many beautiful colors of naturally brown sandstone that you can avoid buying a pigment and use the natural colors of clays like tucker's Mid red for example.)

Starting from the top left in a clockwise direction: Praseodymium Yellow, Bermuda, Dark teal Green, Mazerine Blue, Chromium Violet, Black, Dark Red, Mango, Orange ', Pink.

* A small hole will allow them to be stored as a "necklace", but when you have many like me it is easier to consult when they are free so I keep them stacked in the order of the chromatic circle.

how to make color charts and develop your own palette

Now that you've purchased all of these beautiful colors, it's time to test them out! You’ll probably want to start creating right away, but it’s very common to have very disapointing and you want to find it out before spending all this time on a complex nerikomi piece. I ALWAYS test the pigments that I buy even if I know them well! Pigments are formulations of metallic materials extracted from nature, and can therefore change depending on the source. Also, mistake is human: the people who send them to you could have misplaced the labeling ... I will never stress this enough: ALWAYS TEST!

When I started I was doing my tests a bit haphazardly but I developed a method that I find very functional so to avoid trial errors I’ll give it to you here step by step:

(Pssst: other ceramists will have other methods that work for them, mine is not necessarily the best but it works great for my needs)

  1. I make a large slab of clay, leave it to firm up until leather hard consistency and cut as many pieces as I have stains to test and a few additional pieces to test blends. (about 5 cm by 5 cm, or slightly larger)

    (wear a mask for steps 2 and 3!)

  2.  I weigh 50 grams of porcelain slip per color to be tested, reserve in small pots (image # 1) . (I keep more on hand for testing dilutions)

  3. With a lab scale (a kitchen scale will not be precise enough!) I weigh 10 grams of each pigment. I dump them over the 50 grams of slip and I IDENTIFY with a masking tape all the containers. It’s very easy to get lost once they’re mixed.

  4. I wet the powder with a sprayer, when you no longer see powdered pigment mixing well with a stiff bristle brush.

    (put all the powders aways in a safe spot to avoid any accident before the nest steps, mask not needed anymore)

  5. I sieve the wet mixtures in a test sieve, and pour it back into the identified pots.

  6. I engrave the test plates: on the back I write the name of the pigment and in front I divide the surface into 4 equal strips. (I engrave small lines) You can also only engrave numbers to identify and write the complete informations in a notebook for later reference, but I like to write everything, that way I do not need to look for my notebook each time I consult my samples.

  7. One color at a time, I paint the first line of the color chart. (first line will be 20% because there is 10 grams of pigment in 50 grams of slip)

  8. I weigh the remaining mixture and I put as much porcelain slip to dilute my concentration in half to 10%, and I paint the second line.

  9. I put a spoon of this mixture at 10% aside on a plasterboard to have a swatch of stained porcelain all the way through. (image 3) I continue the dilutions in the same way for the other two lines, 5% and 2.5%. To avoid having large volumes of colored slip at the end, I only take spoons to dilute. (1 spoon at 10% and one spoon pure= 5% mixture)

  10. After, I put all the leftovers of dilutions together and it makes a slip at 8-10% concentration. I keep it aside to test some blends later.

  11. Once the process is done for all colors, I test blends. For my blends tests as there is often a lot of information to note I do it in my notebook. I only engrave the date and the number of the test. In my notebook I will write for example; Test # 1: 2 spoons of praseo yellow # 6450 at 10% + 1 spoon of rose # 6020 at 10% + 1 spoon of red # 6021 at 10%. In general in my blends I only test one dilution so I paint half of the swatch, and the other half I put as much slip to have the test at approx 5%.

  12. Leave to dry and apply a transparent glaze to half of the swatch. (this can be done in a single firing (no bisque) to save time)

     

N.B .:

  1. * Dark colors like Mazerine blue, black, dark teal green start at 10% going down because they have a much stronger coloring power than pinks, reds, yellows and purples.

    * Purple is the least powerful color: even at 20% you will have a rather pale lilac. If you want a darker purple it will have to be tested in blends with blue but beware: always a lot more purple than blue because blue is more powerful! If you are looking for a shade of purple try around 10 to 1 and variations around that.

color the clay balls and conservation

Now that you have your tests, you can see at what percentage you like the colors. Is it 5%, 10% or would you like something in between? it's simple, do it at 7.5%!

  1. Weigh and make a pigment slurry:

    I always make my balls at 1 kilo. It's very easy to calculate and I find it to be the ideal size for storage. So if I want a 10% yellow porcelain ball, I only have to weigh 100 grams of pigment, no need to reach for my calculator. To avoid the dust I weigh in container that have a little water (make sure to do the tare before of course) However, with this method you have to be careful because it will be difficult to remove some if it is wet. You can also avoid weighing the pigments and make a rule of 3 with the weight written on the jar when it’s new. At sial the pots are 113 grams so to have 10% you will need 1130 grams of clay. *Not weighing decreases the handling of the powder and therefore your risk of breathing it. When I do not weigh I put the whole jar directly in a small container of water and I let it absorb slowly.

  2. Incorporate the wet pigments in the clay:

    The ideal consistency is like yogurt, it must be fluid enough not to agglomerate in clumps but thick enough to spread easily. I make rough slabs, I paint them with one coat, I roll, a few kneading strokes, and I repeat until I’m out of pigment slurry. At the end, I knead real good to homogenize. IMPORTANT: Do not try to put everything at the same time or you will have a MESS, the pigment slurry will wont mix with the clay and you will have splashes ... it takes at least 3-4 times or more depending on the quantity.

  3. Store and save your colored clays:

    I put the balls in freezer-type ziplock bags (1 kilo fits perfect in the size M). They are robust, washable and reusable versus conventional ones that rip easily. Write on the bag what it contains: the name, the date and a reference number. (For example: 02-02-20, # 1: Praseo Yellow 10%.) Keep the bags in airtight containers.

  4. Make test tiles!

    Yes Yes boring I know testing again ... it is very easy to have variations or to make a mistake between a mixture in 50 grams versus in 1 kilo ... While making your designs it is important to see exactly what the end results will be. You can simply engrave the numbers you wrote on the ziplock bags (#1) and then when it comes out the kiln you can add informations with a sharpie: 02-02-20, # 1: Praseo Yellow 10%.

now you're ready to create with colored clay!

Whoa that was a lot! You do not need to learn all of this by heart, you can keep this article bookmarked for future reference... When I started I knew nothing about all of that… I did not attended a colored clay workshop at all neither knew of all the ressources I know today like the facebook group Color In Clay by example. I accumulated all these tips and tricks in 3 years of experimentation so if I can avoid you unnecessary mistakes I’ll have done my job. But I think it is also necessary to allow yourself to instinctively get to know colored clays by feel and trial and error. This is how we learn and develop our own style. I myself borrow techniques here and there but I am far from working in the "rules of the art" of Nerikomi and that is what gives my special touch to my pieces. In future posts I will give tutorials to get special effects like marble and granite effects, gradients, cane patterns and much more. To go faster, you can look at polymer clay tutorials on Youtube: most of the techniques also apply to clay and it is very easy to understand because it is instant unlike clay where you will see the result only after several finishing steps and two firings. I hope you feel more confident to start your own colored clay journey and do not hesitate to leave a comment if I left something in a grey zone.

xx

Marina

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