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Art that rocks

by Elena Johnson
| May 27, 2020 1:30 PM

Recently I was working on this year’s edition of Discover North Idaho (temporarily renamed Explore North Idaho, because we’re as confused about 2020 as you are), when I was beefing up an entry on Treaty Rock Park.

(I know, where’s the mystery? The magic? No one wants to see how the publications get made. Gross.)

If you live in a place for all, or most, of your life, you’re supposed to know the names of most things and places around it.

But I don’t.

I still refer to things by landmarks or childhood memories. Until a few years ago, English Point was “You know, where we used to go for walks sometimes on Saturday mornings and also Aunt Shahla went with us once?”

And yes, I am also the person who can’t give you directions because I “just go straight for a while until I hit the really pretty willow tree and then I think it’s on the right a few blocks after that.”

What, you mean you don’t remember places by whether you pass a barking dog on the way?

Anyway, if you’re like me, Treaty Rock Park is the one with the big rock that has a treaty and some really cool pictographs on it. You won’t miss it because it’s covered with glass and flanked by signs. Also, there’s a little trail in the park.

It’s also the one at 705 N. Compton Street in Post Falls.

Somehow, I’ve missed this one for a long time. I know that partly because my mental register is lacking the above description and partly because I love me some rock art.

After I took a recent opportunity to study art conservation, I began to love it even more.

Rock art, as you probably guessed, is any art done on a rock. But we normally use the term for specific kinds of art (no disrespect to those of you painting rocks at home!)

A lot of rock art is pretty old. It doesn’t have to be, but nifty tools like paper and plastic make rocks a less necessary and less useful choice. They aren’t necessarily the best surface for drawing either.

But what makes pigment stick to a rock or similar surface – like a stone wall?

In simplistic terms, petrification.

In more descriptive – but equally simplistic – terms, the right kind of pigments mixed with the right kind of materials can actually become a part of stone during its application and drying process.

The pigments – the basis for any paint – have to come from minerals and are found in rocks or soil, including clay. Think yellow ochre or a siena brown. Or the red ochre used at Treaty Rock.

The pigments have to be attached to a sticky binder. Crushed up minerals make a powder and they need something to help them stick (or bind) to a surface. This also helps turn the pigment into a paste – a paint that can be applied in pretty patterns.

(If you’ve ever tried to get glitter to stick to a single surface and nothing else, you can already understand why paints are way better for making designs than powders.)

Egg whites, sap, animal fat and bone marrows, spit and even blood are pretty common binders, along with a form of hydrated (as in wet) lime (as in, limestone – not the citrus fruit).

You can make a pigment stick for a long time without limestone (or calcium carbonate), but it’s going to be much closer to permanent with some form of lime added. It’s the magic ingredient for petrification.

The whole process is technical, but basically you mix these things together and apply them, and bam! It dries and becomes rock in the process. Although some mixtures and applications are more effective than others. (If you want to understand the chemistry behind this, look up “cycle of lime”.)

The result is a design that’s part of the rock itself.

Somehow, cultures all over the world figured this out – perhaps without meaning to.

So when you see rock art, like the pictographs at Treaty Rock Park, there was probably some petrification going on.

You’re not looking at art on a rock, you’re looking at rock-art, literally.