Tuesday, 17 April 2012

Alum

alum, in powder ( left) and lump ( right) form
Alum is the third most important substance in marbling, after the gall and the size. It makes the colours adhere to the paper.
 Marbling on tragacanth does not requore alum  but the paper must be dampened slighly to accept the colour. The reasons behind this I have not been able to find out,( but it might, historicaly have something to do with the fact that the paper used being more absorbent). However, marbling on Carrageen requires the substance to be dissolved in water, and sponged on the paper.  The process imparts some degree of acidity to the paper .  As a result, some binders tend to avoid them. However, for odinary uses, the acidity is negligable.
There are two kinds of alum , potash alum (potassium aluminium sulfate), or just plain alum ( aluminium sulafte). Both work well.

Take a heaped tablespoon of powdered alum , and dissolve it in a cup of hot water. Stir to dissolve. ( this has a tendency to heat up the water, so be careful) .
Now, take the sheets of paper you intend to marble, and mark the side you do not want to marble with a pencil. This helps you distinguish which side to lay on the size.

Soak a sponge in alum, and apply it to the side that is not marked. Lay it flat to dry.

The paper can be marbled when it is dry, or slightly moist.

3 comments:

  1. Hi Matthew, Thanks very much for blogging about paper marbling. I just stumbled across your website and was so pleased to find out that you're a fellow New Zealander. I've been marbling on and off for about a year with varying results, the main problem being that I can never seem to get brilliant saturated colours consistently. Colours just seem to either wash off or wander around the rinsed, marbled paper and I'm at a loss of what to do!
    I'm wondering if it's the aluminium sulphate that I use, and perhaps how I'm applying it? I use 1tbs per cup of water, and have increased it up to 2tbs without much difference. I have noticed however, that marbling in the middle of the day such as today (late August) in Auckland seems to help, but I'm still hoping to to achieve brighter tones than the washed out ones I'm getting.
    I have a ton of colours to draw from, both acrylic and good quality watercolours, just in case you are wondering if it's a pigment problem.
    Would be ever so grateful if you had any thoughts about my problem.
    Thanks heaps!
    Kind regards,
    Liyen

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  2. Today I tried for the first time to marble paper.
    I used a guar gum based size and a non treated paper with acrylics.

    The paper I was using was rely porous and I think this helps A LOT.

    Are you using art papers or regular paper?
    A 100% coton paper for engraving or watercolor the results should improve

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  3. Handmade water color paper...is a good choice.. Don't for get to thinker water with corn starch..it gives the paint more surface to float on near the top..

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