Creating your own oil paint: Research
Through #150 the topic came up that we might want to create our own linseed oil paint - for the fun of it and to save money.
Here we go:
Pigments (white paint)
In an oil paint, there is about 50% pigments inside the oil.
zink oxide absorbs UV and is white colored. In thin oil paints, it might have a bluish character. All/(most?) zink oxides contain small amounts of lead - typically around ?10 mg/kg? (0.001%). There is a pdf from a pigment manufacturer that seems to provide some hints, e.g. suggests using a "Glasläufer" to mix oil and pigments (https://www.kremer-pigmente.com/media/pdf/46300.pdf) (https://de.wikipedia.org/wiki/Glasl%C3%A4ufer) Price: 7-12€/kg at 10kg. Not very clear to me if the normal "Zinkoxide" (pharma/chemical ingredient, 10-50% cheaper than the pigment stuff) is enough or it needs to be "Zinkweiß" which might be much finer.
Also called Titanweiß.
Available very cheap or expensive (https://paintsystems.com/Titandioxid-Titanweiss-Rutil-TiO2-Farbpigment-10-kg 4€/kg or from kremer for 11€/kg again). Again, nice pdf from kremer (https://www.kremer-pigmente.com/media/pdf/46200.pdf). Some health sites say it is not good to have it in food :-)
Sikkative / additions that make it dry faster
- not really necessary, as it will only make the paint dry faster. If there is enough fresh air, a paint without this should dry within a week, with in a day.
- Alternative recipe: Boil the oil until it just starts smoking, keep temperature for 2-3 hours. Let cool down for a day, heat again to 200 degrees for 2-3 hours. (http://rolfrost.de/firnis.html)
- To me it sounds like the sikkative are not a very nice thing.
- Alternative: Leinölfirnis is not that much more expensive than leinöl.
http://www.farbmanufaktur-werder.de/catalog/product_info_texte.php?text_id=66 suggests using pure linseed oil as a first layer. Goal is to get as much oil into the wood as possible, the goal is not to create a layer on top. Drying time: 2 weeks. Afterwards, add the pigmented paint. The pure oil would not last very long, but the pigmented one acts like a protective layer on top. Can be washed and repainted as often as you like.
Oil usage: 0.1l/m² for the first layer. As the paint layer is only ~0.1mm thick (and does not go into the wood anymore because that is saturated), the oil paint should last for 10m² per liter
Simple price comparison:
- White oil paint: 40..80 € / liter
- Self made oil paint: 6€/liter firnis, 10€/kg zinc, 4€/kg titandioxide -> ~12-15€/liter paint + mixing work + trying out :-)