I have been trying to make my own linseed oil paint by adding pigments to boiled linseed oil. I have added around 500 g of titanium oxide per litre of BLO and around 125 g of zinc oxide (to help speed the drying). The paint mixes well and seems to go on ok but even after leaving to dry for a week or so, the colour can be rubbed of with a cloth (as in you can see white come off on a dark coloured cloth).
I tried to dilute the white I made with more oil and tried adding more zinc oxide (in two separate batches) but the problem still persists.
Any clues would be very welcome!