As we cannot readily obtain ammonium caseinate powder in Australia, the preparation has to start from scratch – you have to make casein or find some casein powder. After that you have a choice of reagents to get to ammonium caseinate.
Should you have access to casein powder, the quantity of powder mixed at about 1:5 with water appears to be the same as moist, crumbly casein. But you will have to experiment.
The reagents I will describe are cloudy ammonia and ammonium carbonate. These are ones I can readily purchase in this country.
Using Cloudy Ammonia
Clear ammonia is difficult to get in Australia so I experimented with cloudy ammonia – that is ammonia that has some soap added for cleaning purposes. The North American thinking is that you cannot use cloudy ammonia for casein printing because of the pollutants. But you can see from Image 1 that it works quite well.
10 grams of crumbly home made casein1.
5 ml of water
5 ml cloudy ammonia
Add the water to the casein and mash thoroughly with a spoon. It will not dissolve but the water and casein are well mixed. Everything works best if the temperature of all mixes is raised to and maintained at about 600C.
Add 2ml of the cloudy ammonia and stir. Make sure the ammonia is well distributed through the casein.
Leave sit, stirring occasionally. Periodically, smell the mixture to check if there is an obvious ammonia smell. When there is very little smell then add another 0.5ml of ammonia and stir. Repeat this until there is a faint residual ammonia smell – this could take a few hours. This tells you that all the casein has reacted with the ammonia – which is what you want to achieve.
The ammonium caseinate will have a thick, glutinous consistency. It will most likely smell of ammonia but this does not seem to matter.
Dilute this ammonium caseinate mix about 1:1 with water. Experimentation is needed.
Unlike gum arabic, you cannot premix casein and pigment and then store it. It will go off. So you have to mix the coating medium as you need it – but you can, obviously, mix a working quantity for a couple of day’s work.
I use 10% Potassium Dichromate 1:1 with the medium for coating. This is purely a personal preference. Try out both Ammonium and Potassium Dichromate at different concentrations.
Using Ammonium Bicarbonate or Carbonate
As far as I can determine, you can use either Ammonium Bicarbonate or Ammonium Carbonate with the same recipe and process. The resulting ammonium caseinate is thinner than that produced with cloudy ammonia.
10 grams of crumbly home made casein
5 ml of water
3 grams Ammonium (Bi)Carbonate
15 ml very hot water – but below boiling point
The ammonium carbonate is difficult to dissolve. Mix in a container that will stay hot and in which you can vigorously stir or shake the mixture.
In another container, add the water to the casein and mash thoroughly with a spoon. It will not dissolve but that does not matter.
Pour the ammonium carbonate mixture onto the mashed casein and mix thoroughly. Bring the temperature up to about 600C and maintain at that level until all the curds have been absorbed by the ammonium carbonate. This can take over and hour.
This version of ammonium caseinate is usually of the right consistency to use without dilution.
Unlike gum arabic, you cannot mix ammonium caseinate and pigment and then store it for later sessions. It will go off. So you have to mix the coating medium as you need it – but would can, obviously, mix a working quantity for a couple of days’ work particularly if you store it in the fridge.
I use 10% Potassium Dichromate 1:1 with the medium for coating.
1. The degree of dryness I am referring to is when you have a mass of casein that, when squeezed between a couple of sheets of newsprint, leaves only a small amount of dampness. The external paper has very little dampness.