Hello chemistry nerds!

I got into dyeing, first using commercial products, then experimenting with DIY vegetable-based dyes, because if there's a more expensive and labour intense alternative to buying a ten dollar product, I'm all over it. Naturally, I started extracting lake pigments to make paints out of my used dye baths.

Before you say it, yes! I do want lower quality paints that fade faster and take two days to make.

I use alum (aluminium phosphate) and soda ash (sodium carbonate) to precipitate the pigment, followed by drying and grinding.

Since this journey began I noticed some dyes just won't work for pigments. I tried hot, cold, waiting, stirring, light jazz, more acid, more base, but the bitches won't precipitate. Cranberries were my most recent failed pigment (but they dyed real nice.) There was lots of colour left, and I even tried a new dye batch with fresh cranberries, but it had the same result.

SO! I'm wondering:

1. What makes a dye substance a better candidate for a lake pigment? Are there chemicals the alum can latch onto easier than others?

2. If alum doesn't work, could a different metallic salt work better?

3. Why does every blog say not to use your dye equipment for food? What if I clean it super well?

4. Are there other chemicals I can try? For funzies?

5. Are there any other cheap, convenient products I can replace with five hours of destroying my kitchen?