Making —Purple watercolour paint



Current procedure — last updated 2. August 2022

  1. Mix the watercolour paste
    1. Wear a mask. Go outdoors - this can be very messy.
      Pour the medium into the stainless steel container first.
    2. Measure out the powdered pigment.
      Add about a third of it to the Blender Ball, and then top off with about 250ml of medium.
      Seal it up and shake back and forth 60 times.
      Repeat twice more, and then pour in the remaining medium and shake to roughly rinse.
    3. Start dispersing, using a dispersion disc in a drill press.
    4. Cover the bowl while dispersing to limit the dust.
  2. Mill the paste
    1. Set the fast rollers to 6 mil, and the slow rollers to 6 mil.
    2. Prepare two large bowls for use. Find a stand to raise up the bowls to catch the paint to reduce splashing.
    3. Use a nail brush and water to clean the rollers at the end of the first runs.
    4. Put through the mill for 16 runs.
    5. Test for grind at the end of each second run.
  3. Package into pans
    1. Put into a Kewpie mayonnaise bottle with a funnel
    2. Line the bottom of 2 cookie sheets with newspaper
    3. Arrange the 350ish empty 2ml half-pans into rows
    4. Fill the pans to the top using a pipette set to 2.2ml
    5. Allow to dry, and then top off
    6. Allow to dry, and then package into wax paper bags

Drapak’s manufacturing notes

1-2. August 2022 (Emanicipation day) — 150g pigment to 1000ml of medium
Pv19 powdered violet pigment: 150 grams × $0.174/g = $26.10
Watercolour medium 1000ml × $26.10/1000ml = $26.10
Number of pans filled 312 pans × $0.08/pan Cost of pans = $24.96
Total for materials = $77.16 Material cost/pan = $0.247
Time to mix 15 minutes
Time for pre-dispersion XXX minutes
Time to mill 150 minutes
Time to dispense 150 minutes
Total time 315 minutes
Final grind size 15-25µm
Time spent per pan 1.01 minutes × labour rate $0.445/min= $0.45
Total cost/pan = $0.69

Today I used the protein shaker cup to get the pigment wet. It worked beautifully. I still worked outside. I measured out the 150g of pigment before beginning.

I mixed the medium and pigment in four steps. For each one, I put a scoop of pigment in the shaker, and then I filled the shaker up to roughly the halfway mark with medium. I shook each batch for about 90 seconds, and then poured out the mixture into a mixing bowl. The whole process cleaned up very easily. I am hoping that the cyan will mix nearly as easily.

Milling went OK. I only did 9 runs, which I suspect may have been low. There was almost no gumminess on the rollers, and the pigment went through without any real trouble.

Dispensing took a very long time. I topped off the previously filled pans with 1.0ml of paint. Then I filled the new pans with 2.0ml of paint. I dispensed the next day, and I found that some of the milled pigment paste had settled to the bottom of the bowl. I used a toothbrush to stir this scrub this loose and stir it up.

My overall impression is that this is quite a granular pigment, but I also have a sneaking suspicion that it could be dispersed better, although I am not sure how.

17-18. July 2022 — Mixing ½ cup portions = 8 cups total at 1:2
Pv19 powdered violet pigment: 160 grams × $0.174/g = $24.23
Watercolour medium 4 cups × $11.86/4 cups = $11.86
Number of pans filled 283 pans × $0.08/pan Cost of pans = $22.64
Total for materials = $58.76 Material cost/pan = $0.207
Time to mix 15 minutes
Time for pre-dispersion 60 minutes
Time to mill 120 minutes
Time to dispense 60 minutes
Total time 255 minutes
Final grind size 20-25µm
Time spent per pan 0.901 minutes × labour rate $0.445/min= $0.401
Total cost/pan = $0.608

I am making an experimental batch of pigment to get back in the groove. I weighed out the pigment into a bowl before adding to the crucible. This time I added 1ml of ox gall to act as a wetting agent. I also decided to whisk the pigment outdoors. This took about 5-10 minutes.

I would say that it made the most sense to dump the pigment in all at once. It also helped to whisk the mixture mostly around the pigment/medium border. I covered the top of the crucible with a gloved hand to reduce flying powder.

When done, I put my largest dispersion disc in the drill press with a wooden board underneath. I spun it at the second slowest rpm setting with a cardboard dust cover for 60 minutes, which seemed to be very effective.

I sorted random hardware while the paint dispersed in the background. Two birds with one stone! I am hoping that the extra time on the drill press will help reduce the time needed on the three-roll mill.

I ran the mix through the mill 16 times. The drill press helped to disperse the mixture very well, although it did leave a paste on the bottom of the container.

I freed up most of this by re-whisking it. In the future, I will move the dispersion disc around the bottom before milling in order to loosen the paste up.

I tested the grind size after the 12th run, and it was quite good - 20-25µm. I just kept going to get to the established 16 runs because the runs were so quick.

In the initial runs, some of the slurry was lost as it ran through the slow rollers. It collected in the pan below, and much settled out. When I discovered this, I reran that matter, but some was lost. I recommend closing the slow rollers to 6mil.

The clean up was terrific.

Dispensing into pans was pretty decent. I used the 2ml pipette to dispense into the pans. I only dispensed one layer, so I will have to make another batch of paint to top them off when they dry.

Dispensing was accurate but slow. I used 2ml to dispense into the empty pans, although they were a little less full. Try 2.2ml?

TODO: Don't forget to add the clove oil to the last run through the three-roll mill.

13. March 2022 (March Break) — 2:1 medium to pigment

3 cups (240g) of violet ($55.70) + 6 cups of medium ($17.21) = $72.91 / 480 pans = $0.152/pan

Wow. Stirring REALLY does not help. Magenta really needs to be whisked into the medium. 15 minutes of whisking was better than 2 hours of using the lab mixer. I used the mixer after whisking, which is helping the dispersion. The powder is quite heavy, but still use a mask. The mix is currently very very dark - I am very curious to see how this works when it is fully dispersed. I added a little of leftover completed watercolour using the Kama Pigments dispersion, and it was much lighter and intense than the whisked and mixed batch. Some of the pigment did clump and stick to the bottom of the mixing bowl before I began the whisking, and the material does seem to want to foam.

Later - Oh god that was rough. I ran the batch through the mill 16 times, and it still did not develop colour well. I used a 7 mil gap on the slow rollers and a 6 mil gap on the fast ones. I could see little half-moons form on the apron when the particles were crushed and dispersed. This happened more with the material at the end of the run than at the beginning.

The process took 5 hours. The grindometer did show a difference between the batches. I went from a particle size of about 30µm to 15-20µm. The result was a duller blue-magenta mix that had a granular appearance. Compared to the dispersed mixture from Kama, this was a real disappointment for a lot of work.

Mechanical dispersion is not all that is needed, and I will need to use some chemical dispersion.

Making a stack of wood to hold the bowls was a great idea, and made clean up so much easier. I think that running the mixer in the drill press at a higher rpm would help mix things better.

Using an old toothbrush to clean up the mill was very helpful. So was having a sacrificial towel on the floor. Even though it was a long, tough run, clean up was very reasonable, and there was not a lot of mess.

TODO: Add chemical dispersant. Try ox gall and Orotan. Start the rollers off at 7/6 mil. Run the drill press faster. And use less clove oil. Use a toothbrush to clean the mill, and a sacrificial towel for the floor as well as lots of newspaper on the counters.

11. Oct 2021 — ½ cup total of Quinacridone Violet (PV19)

Mixing: I placed the medium first into a mixing bowl, then placed the magenta pigment on top. I originally started to mix with a spoon, but it really was not working. I switched to using a whisk, and this went much better, although the paste was pretty rough and there was a lot of dry powder floating on top.

Milling: I set the roller gaps originally to 15 mil each. I did not have any trouble with pigment falling through the rollers. A fair amount of the pigment dried on the rollers as well. I put the paste through three or four times. Afterwards, I learned that the dispersion was not good enough: there were quite a few small clumps.

Mixing TODO: Mixing a larger batch would make a lot of sense. Use a whisk right away.

Milling TODO: try starting the mill off at 15 mil gaps on the slow side, and 10 mil on the fast side. Using a spatula to scrape out the mixed paste helped a lot. I will have to put the paste through the mill more times.

Next: try milling magenta again. Try a 3:2 medium to pigment ratio. Actually, let’s try a 2:1 ratio.