- PPE: mask, gloves, and apron
- A measuring cup
- A digital scale
- A stainless steel bowl (1500ml+)
- A stainless steel hopper (1500ml+)
- Drill press with dispersion disc
- A three roll mill
- Small 1ml watercolour half-pans
Current procedure — last updated 26. August 2022
Mix the watercolour paste
- Measure out the powdered pigment and place it in mixing crucible.
- Then pour the medium on top of it.
- Start dispersing, using a dispersion disc in a drill press.
- Cover the bowl while dispersing to limit the dust.
Mill the paste
- Set both rollers to 6mil.
- Prepare a large bowl and a hopper to use. Find a stand to raise up the bowl to catch the paint to reduce splashing.
- Use a nail brush and water to clean the rollers at the end of the first runs.
- Put through the mill 10 times.
- Test for grind at the end of run #4, #7, and #10.
- At the start of run #9, add one drop of clove oil for 250ml of total medium (100ml mix = 4-5 drops) Add the oil to the paste on the slow rollers, rather than in a bowl on in the hopper.
Package into pans
- Arrange the 1000ish empty 1ml half-pans into rows on cookie sheets
- Fill the pans to the top with 1m each
- Allow to dry, and then package into wax paper bags
Drapak’s manufacturing notes
5. September 2022 (Labour day) - 79g pigment: 500ml medium
|Pw6 powdered titanium white pigment:||150 grams||× $0.049/g =||$7.35|
|Watercolour medium||500ml||× $23.09/1000ml =||$11.55|
|Number of pans filled||703 pans × $0.08/pan||Cost of pans =||$56.24|
|Total for materials =||$75.14||Material cost/pan =||$0.11|
|Time to mix||10 minutes|
|Time for pre-dispersion||20 minutes|
|Time to mill||90 minutes|
|Time to dispense||60 minutes|
|Total time||180 minutes|
|Final grind size||5-15µm|
|Time spent per pan||0.26 minutes||× labour rate $0.445/min=||$0.11|
|Total cost/pan =||$0.22|
I decided to double the density of the pigment in this batch to 300g/1000ml. It seems to be working better.
This was a better run. I did 10 passes through the mill. It was a half-batch, but it worked.
The plunger on the hopper stuck during the first three runs.
This seemed to sort itself out as the paste become more finely ground.
The schmoo dispenser also worked out very well.
25. August 2022 - 150g pigment: 1000ml medium
|Pw6 powdered titanium white pigment:||150 grams||× $0.049/g =||$7.33 * 650/1000 = $4.76|
|Watercolour medium||1000ml||× $24.43/1000ml =||$24.43 * 650/1000 = $15.88|
|Number of pans filled||651 pans × $0.06/pan||Cost of pans =||$39.06|
|Total for materials =||$59.70||Material cost/pan =||$0.092/td>|
|Time to mix||0 minutes|
|Time for pre-dispersion||30 minutes|
|Time to mill||70 minutes|
|Time to dispense||50 minutes|
|Total time||150 minutes|
|Final grind size||10-20µm|
|Time spent per pan||0.230 minutes||× labour rate $0.445/min=||$0.102|
|Total cost/pan =||$0.194|
Well, that was an adventure!
Milling the white went very well. Titanium white is a heavier pigment, and does not fly into the air like an organic pigment. So it is much nicer to work with. I still pre-dispersed it for a while while preparing the pans for filling.
The pigment itself was quite grainy for the first few runs, and required a number of extra runs to smooth out. In the end, I ended up doing 10 runs. However, the paste itself was quite liquid, so each run went very fast. All told, the paste is very fast to run.
I think that the final paste is a little light on pigment for my liking, though, so I am thinking that the next batch should use 200g of pigment.
This was the first time I was able to use my homemade paste dispenser, and it worked beautifully! I was able to fill 651 pans in less than an hour, with no mess, very consistent results, and fast! I think that this will really help to take the cost down in the future, so this is a good investment.
However, there was one very bad thing. At one point, I was pouring the white into the hopper, and I failed to notice that the plunger valve of the hopper had stuck open. The white pigment had overflowed everywhere. Over the rollers, overfilling the tray underneath, leaking all over the mill, and covering about 1/3 of the tray at the base of the machine.
Am I ever glad I put that tray underneath the machine! Otherwise, the white paint would have flowed all over the floor!
The clean up ended up taking about an hour, and I lost about 350ml of paint. White paint even got into the coolant bath, turning the mixture milky. The quality of the paint was amazing, which made it a real pain to clean up! That makes sense, but boy was it miserable.
However, the mill is now very clean, and this gives me a chance to do some maintainence. I will take the opportunity to add engine coolant to the coolant system to battle rust. And I will shoot some grease into the bearings as well. Goodness me!
Even though the paint was very rich when wet, it seems to be drying very thinly. I will top it off with a richer mix.
17. March 2022 - Making ~2 cup total
1:1 mix — 250 ml of medium ($3.02) and 250 ml ($10.50) of dry titanium white = $13.52/300 ish pans = $0.045/quarter pan
This was so dreamy to mill. I began by putting the 250ml of PW6 into a stainless steel mixing bowl, and then I added 250ml of medium and whisked the two together. I ran the batch through the mill 8 times with a 6mil gap on the fast rollers and a 7mil gap on the slow rollers, and the result was very very creamy. The resulting grind was about 10µm, and was a terrific consistency to dispense into pans. I was able to fill one entire cookie sheet full of quarter pans (1mL) with the resulting mix. The paint seems smooth and opaque.
TODO: Increase the proportion of pigment to reduce stickiness. Perhaps 3:2?
11. Oct 2021 - ½ cup total
Mixing: The pigment mixed fairly well into the medium. It started to wet fairly quickly. I alternated with medium and pigment until done. The result was light grey with a few undissolved chunks.
Milling: I set the roller gaps originally to 20mil each. I had some trouble with the pigment falling through the gap and collecting in the plate underneath. A fair amount of the pigment dried on the rollers as well.
Mixing TODO: medium first, and mix in pigment. Allow to sit for a while to see if it wets better over time. Mixing a larger batch would make a lot of sense.
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.