Will Epsom Salt Work

I've used alum solution in my painting quite a bit.  It is affectionately called the Ancient Chinese Secret Solution by me.  Alum is used as a sizing agent for Xuan.  I understand alum is used as a mordant in dying.  I use it to function as a masking fluid by exploiting the fact that alum treated Xuan is less absorbent,  thus the treated area will reveal with a different gradient when stained. 

I typically would paint on the back side of the paper with a alum infused brush.  The brushstroke will reveal a clear margin when a different color is painted over it; as long as that color is not too strong to obscure the margin.

Here's an example of the margin

I've also used this technique to create a blurry image by first painting with alum on the reverse side of the paper, allowing the brushstroke to show through the top side.  I then go over the top side with a darker color, being careful to not totally obscure the original brushstroke on the back side.  The resulting image has that interesting back lit effect and suggests a 3 dimensional perception, especially when viewed from a distance, or by squinting one's eyes.

Here's another example of painting done with alum solution.  Its role in making the paper less absorbent is exploited to the extreme by functioning as a masking fluid.  It was used to paint in the snow.   Obviously it is well suited for high contrast work like this one.

I was contemplating painting a desert scene and I was interested in a novel way to depict the wind generated ridges on the sand dunes.  I didn't want to paint these wavy ridges with hard ink brushstrokes.  I therefore turned to my secret solution and envisioned the clear margins left by such brushstrokes would be more enigmatic and evoke more drama in my painting.

But I ran out of my Ancient Chinese Secret Solution.

I resorted to my daft antics. 

I recall a leftover bag of Epsom salt from when I sprained my ankle.  Epsom salt is magnesium sulfate.  Could I substitute Epsom Salt for Alum, which is aluminum and potassium sulfate.  I recall reading about using copper sulfate as a mordant, so why not magnesium sulfate?

I rolled up my sleeves and went to work.  I prepared a saturated solution of Epsom salt.  My experiment involved painting with the Epsom salt solution in raw and semi-sized Xuan.  I painted on the top side of the paper, and on the back side of the paper to see if the reveal is different.

Here is the result of painting on regular raw Xuan.  The top image is painting the Epsom salt solution on the top side of paper; bottom image is painted on the back side.

Here is the result of painting on semi-sized Xuan.  This paper is less apt to absorb liquid because of the sizing, therefore I wanted to see what effect my concoction will have, if any.

So when applied to the top side of the semi-sized Xuan (top image) Epsom salt seems to have a smidgen of effect.  I think I can make out a semblance of a faint margin.

As you can see, Epsom salt solution failed as a candidate for alum substitution.

I know what will be on my shopping list now.