Tinting Slip

Hagen-Renaker tinted their slip almost from the beginning. The colored slip allowed them to just overspray accent colors and not need to paint the entire piece. This was very time-saving, but there were trade-offs, as I am finding now.

Colored slip is made by mixing the regular white slip with minerals or oxides. These are actually ground up rocks, basically, like manganese or iron oxide. They come in powdered form and are often called "mason stains". They can be used for many types of pottery applications, from tinting slips and clays, including stoneware, to tinting glazes and even concrete! (Thus the "mason") The oxides react differently according to the usage and firing temperature, so there are different charts showing applications for low fire and high fire.

Using a gram scale, (feeling like a drug dealer), you measure small quantities of oxide into a little cup. You then add water, enough to make a runny paste, and then when it is well mixed you add it to a specific quantity of slip. After you cast with it, then allow the cast to dry, clean it, bisque fire it, glaze and glaze fire it, you know what color it is. Then you can come back and add a little more, or another color or whatever. I have been testing colored slip for the new horse, Hadrian. He will be cast in a medium golden brown so that only his accent colors (red-brown and black) will need to be applied. This will be easier in the long-run but is certainly tedious and aggravating now!

The bonus is that a large quantity of slip, all the same color, can be made up and there will be very little variation. The horse will already have a base color, and since his base color is in his clay, he will not need those layers of color applied. This will keep his detail sharp, not filled in by the paint. He will also be easier to handle and not smudge the paint.

The trade-off is that in order to sell white bisques, totally separate molds will need to be made just for white (because the colored slip tints the molds... pink Hadrians, anyone?) And totally separate tools and recycling jars will be needed for the casting process. The tint is strong, even a little contamination will go a long way. (Has anyone heard of the "pink-maned H-R Morgan stallions"? This is what likely happened to the paint.) The oxide also makes the clay slightly softer while casting and is easier to break while raw. I don't notice a difference when fired, but Hadrian is a mini with sturdy legs and he isn't likely to be very vulnerable. However, strongly tinted H-Rs are probably a little easier to break because of the tint. That's likely why very few black or dark horses were produced, it takes a LOT of tint to make these strong colors! Not to mention expense, since the black is very costly.

I am looking forward to tinting the slip for Hadrian because he is the very best candidate. He is a Dales pony, so would very typically be solid bay with no white. He is sturdy and has lots of muscle to highlight. His mane and tail look excellent hand painted over the colored slip. (You'll see!) But I don't anticipate doing this often, since it does have a lot of difficulty. However, having the opportunity to do it allows me to explain it to everyone, and thereby learn something new myself. I am looking at my H-R collection in a whole new way...

Hadrian will be offered to the Pour Horse list after March 1st, when the testing is done and the Pour Horse Patter is printed. I'm getting closer on the color but the lag time between casting and glaze fire makes the adjustments slow.  Joanie