Metals & pH Shifters
Metals will fix the colours and modify the colours.
pH shifters will shift the colours but will not fix the colours.
Iron oxide
Iron oxide is used in combination with inks and paints that contain tannin to darken/blacken and make the colour more stable.
Iron oxide recipe
You can make your own iron oxide solution by soaking rusty nails (or other small iron objects) in vinegar for a month.
Iron reacts with the acetic acid in the vinegar very slowly and releases H2 gas.
Iron (II) Acetate, is formed which is soluble in water. I keep my nails and vinegar in a plastic basket with the lid loosely on. It is dangerous to store it in an airtight container as the pressure builds up with the gasses. The reaction is very slow so it is safe to do this in an enclosed environment (I have had a bucket in my studio for years.)
Chemical Equation:
Fe(s) + 2CH3COOH(aq) --> Fe(CH3COO)2(aq) + H2(g)
- The other "rust" formed is probably Iron(III) oxide formed due to dissolved oxygen in the water.
Chemical Equation:
4Fe(s) + 3O2(aq) --> 2Fe2O3(s)
This iron acetate/oxide can be used to darken and fix plant inks. You can use it as a wash over or under your ink or mix it in to the ink. Only a few drops of iron acetate/oxide solution is needed if you mix it in to your inks.
For an immediate solution, you can dissolve ferrous sulphate crystals in water
Keep out of reach of prying hands. Clear labelling is important.
Copper Acetate
Copper acetate is used in combination with inks and paints that contain tannin to darken/blacken and make the colour more stable. Copper will not darken as strongly as iron oxide so some of the original colour will remain. This can be used to modify your inks. For example to turn orange coreopsis ink red. By either adding a few drops to your coreopsis ink, or layering it under or over.
Copper acetate recipe
Soak copper wire in a mixture of half vinegar and half salt for a month or more. Make sure you use a metal free container made of glass or plastic. Avoid contact with this substance as it is very corrosive. You can evaporate this down to create a blue ink. Once a strong blue colour has formed, I like to pour my copper oxide in to a plastic tupperware container and let it evaporate in the air out of reach of children and pets. This is slow but gives a very pure blue colour. This gives the clearest blue liquid. You can evaporate by boiling in a pan. Use a ceramic pan to avoid contamination and corrosion.
Use this as a wash over or under your drawing or as a blue ink in it’s own right.
Aluminium Sulphate
Aluminium sulphate is used in combination with inks and paints to fix and brighten colours.
Option 1. Dissolve aluminium sulphate crystals in water, add gum arabic. Use this as a wash over or under your drawing.
Option 2. Add aluminium sulphate directly to the ink in powder form. Do not add aluminium sulphate to a soda ash ink, unless you would like to make a lake pigment.
Citric Acid
This shifts colours towards yellow/orange/pink. It can be used as a discharge, bleaching out the colour of some inks. It will make lake pigments more smooth by reversing the effect of the soda ash after the pigment has been settled and filtered.
Option 1. Dissolve citric acid in water, add gum arabic.
Option 2. Use citric acid directly to the ink in powder form.
Option 3. Use citric acid directly to your drawing in powder form.
Bicarbonate of Soda
A mild alkali.
Option 1. Dissolve bicarbonate of soda in to some water and gum arabic. Use this over or under other plant inks for colour shifts.
Option 2. Use bicarbonate of soda directly on your drawings in powder form.
Option 3. Add bicarbonate of soda directly to the ink in powder form.