Glue emulsion

[Sam H]

I've been exploring the usage of a glue-oil emulsion for a mixed technique. The recipe I'm trying consists of 1 part methyl cellulose glue (1:25 powder to distilled water), 1 part damar varnish, 1/2 part stand oil, and 1 part distilled water.

I'm uncertain I'm getting the proper result; With the glue, oil, and varnish added, the mixture thickens and has a creamy consistency and off-white appearance. However, once I add distilled water and stir, the oil/damar component turns into a mass of flecks like tiny paint chips and separates.

photo:



Is this supposed to happen? I've tried a number of things - adding damar/oil in different order and different proportions, substituting linseed oil, etc, to no avail.

[sander]

Sam H: I'll leave the technical to others. Just want to say, great photo.

[George O'Hanlon]

First of all, welcome Sam.

This recipe sounds close to the one used by Patrick Betaudier, a surrealist painter who lived in France. The problem you may be experiencing is that you are most likely breaking the emulsion whebn adding more water, because you begin with a water-in-oil emulsion and then by adding more water thereby inverting the emulsion to an oil-in-water emulsion. You must heat the oil phase then add the protective colloid (methylcellulose), and finally contnue heating the emulsion while adding water dropwise with rapid stirring (use a blender or stirrer attached to a hand drill).

[Sam H]

Sander - Thanks for the laugh. At least I'm doing something right.


George - Thanks for the instructions - information on this emulsion seems scarce on the internet. It is indeed a recipe I saved from an old forum posting about Betaudier (I also recall reading you studied with him, if my memory is accurate). Is it necessary to heat to a certain temperature for a certain period of time?

I've tried combining the elements while heating over a primitive hotplate (no temperature control) and encountered the same result, though admittedly I'm lacking a blending element. I notice the original recipe says to combine the ingredients in a blender as well - looks that will have to be my next purchase.

Something interesting I found was that doubling the methylcellulose content prevented separation and the flaked appearance when water was added. Is there any danger from overusage of the MC?

Finally, is there a desirable consistency for emulsions?

[George O'Hanlon]

Yes, I studied briefly with Patrick.

And yes, the amount of methylcellulose can have a dramatic effect on the efficacy of the emulsion. There is no danger in increasing the amount of methylcellulose as long as it is in within reasonable amounts.

Try a stirring blade or paddle attached to an electric hand drill. You can use the drill for other things, which you cannot do with a blender.

I am not sure what you mean by 'desirable consistency'?

[Sam H]

Thanks again, George. By 'desirable consistency', I mean the thickness (viscosity?). Without the additional distilled water it's fairly thick.

[George O'Hanlon]

There is no ideal consistency. However, a thicker consistency is easier to maintain as an emulsion than a thin liquid. Making emulsions is a tricky proposition, even for experienced chemists.