Update docs/assignments/week04.md

docs/assignments/week04.md

@@ -258,6 +258,45 @@ silkscreen_printing_mordant.mp4
 Beware of multiple dips, do not mix the different baths.
 </aside>
 
+ <p style="clear: both;"></p>
+<br/>
+
+### The pigments
+
+Ingredients:
+
+20g of alum
+5g of soda crystals
+200ml of filtered colour juice
+Utensils:
+3 beakers with high rims (the reaction may foam afterwards)
+3 spoons
+1 funnel
+1 mortar and pestle
+1 maryse
+1 balance
+1 piece of cotton to filter the pigment
+1 dehydrator
+Do not mix the spoons as you go along. The amount of water depends on the saturation of the alum as you mix.
+</aside>
+
+Preparation:
+
+1 - Weigh the solid ingredients: alum and soda crystals.
+2- Dilute them separately with hot water (Alum needs more time to dissolve)
+3- Pour 200ml of filtered coloured juice into the high rim beaker
+4 - Add the diluted alum to the beaker
+5- Gently add the soda crystals and mix
+6- Leave to stand for several hours, until 2 phases appear (a liquid and a solid phase)
+7- Place the cotton ball in the funnel to recover the solid phase
+8- Leave to filter for several hours/days
+8- Collect the precipitate (solid phase) with a clean spoon
+9- Put in a dehydrator
+10- Grind it with a mortar and pestle
+Long conservation of the pigment in a hermetic support. Pigments dissolve in oil, not water.
+
+<p style="clear: both;"></p>
+<br/>
 
 ## Documenting experiments