ResolvableOwl
Notorious Lyear
Warining: Rabbit hole!
(lye-based, because you will need some alkali to precipitate the alumina, that's the whole point of lake pigments)
Right now, things are about to escalate once again, the topic this time are lake pigments. Lakes are an age-old technique to convert soluble, organic dyes into insoluble pigments. It is interesting for soapmaking, because many organic dyes are prone to migration, and diffuse through soap over time, blurring sharp boundaries, e. g. within swirls or embeds. Sometimes this is intended, but sometimes you might want to avoid it.
The general principle is that a water-soluble dyestuff is mixed with a solution of an aluminium salt, and then the aluminium is knocked out of solution to form insoluble aluminium hydroxide, carrying the dye with it into a fine flaky powder, that can be dried and used as a pigment. When carried out with wastewater treatment in mind, it is called flocculation, fabric dyers will recognise close relation to the se of mordants.
Literature sometimes also mentions salts of iron, copper, lead or other metals. But I will focus on aluminium because it is one of the, say, less troublesome cations in soap (doesn't proliferate DOS).
The most usually used aluminium salt is alum (potassium aluminium sulfate). Other soluble Al salts will work too. I myself will use aluminium formiate because it is what I have at hand (originally as a textile mordant).
In practice, there are two approaches to end up with flocculated dye:
The online DIY community appears to prefer the alum-alkali process. It's a great way to salvage the remaining colourants in spent dye baths from the drain!
I've posted some success with safflower petals already a few days ago. But foreseeing it will be buried there rather sooner than later, I'll start a new, colourful thread here.
My short-term goal is still the same: fill that awkward red-orange-yellow rainbow gap between alizarin/madder pink and chromium oxide green with soap-fast, non-bleeding, bright and reasonably non-toxic colourants.
(lye-based, because you will need some alkali to precipitate the alumina, that's the whole point of lake pigments)
Right now, things are about to escalate once again, the topic this time are lake pigments. Lakes are an age-old technique to convert soluble, organic dyes into insoluble pigments. It is interesting for soapmaking, because many organic dyes are prone to migration, and diffuse through soap over time, blurring sharp boundaries, e. g. within swirls or embeds. Sometimes this is intended, but sometimes you might want to avoid it.
The general principle is that a water-soluble dyestuff is mixed with a solution of an aluminium salt, and then the aluminium is knocked out of solution to form insoluble aluminium hydroxide, carrying the dye with it into a fine flaky powder, that can be dried and used as a pigment. When carried out with wastewater treatment in mind, it is called flocculation, fabric dyers will recognise close relation to the se of mordants.
Literature sometimes also mentions salts of iron, copper, lead or other metals. But I will focus on aluminium because it is one of the, say, less troublesome cations in soap (doesn't proliferate DOS).
The most usually used aluminium salt is alum (potassium aluminium sulfate). Other soluble Al salts will work too. I myself will use aluminium formiate because it is what I have at hand (originally as a textile mordant).
In practice, there are two approaches to end up with flocculated dye:
- the alkali-alum route, where first an alkaline solution of the dye is made, second the alum is added.
- the alum-alkali route, where the dye is prepared in an (acidic) alum solution, that then is made alkaline to form the insoluble final product.
The online DIY community appears to prefer the alum-alkali process. It's a great way to salvage the remaining colourants in spent dye baths from the drain!
I've posted some success with safflower petals already a few days ago. But foreseeing it will be buried there rather sooner than later, I'll start a new, colourful thread here.
My short-term goal is still the same: fill that awkward red-orange-yellow rainbow gap between alizarin/madder pink and chromium oxide green with soap-fast, non-bleeding, bright and reasonably non-toxic colourants.
