What pigments are not suitable for silicate paints and why?
The following pigments are not suitable for silicate paints: chrome yellow, chrome green, zinc yellow, zinc green, cynober, manganese violet, iron blue and lead white. These pigments change color when exposed to water glass and/or thicken silicate paint by chemical reaction with water glass.
How different types of zinc white are marked in the trade? What are the different types?
Zinc white is commercially marked with seals: White, green and red. The white seal means the highest content of pure pigment and at the same time the highest hiding power, Red – the smallest.
How can you recognize, is the white pigment zinc white?
Zinc white turns yellow when heated, and turns white when cooled. Unlike zinc oxide, zinc white is not colored by sulfur.
What is the difference between zinc oxide and zinc white?
Unlike zinc white, zinc oxide contains lead oxide.
How can you recognize, is the white pigment zinc oxide? Zinc oxide turns yellow when heated, and turns white when cooled. Depending on lead content, zinc oxide is colored – after adding hydrogen sulfide or sodium sulfide – more or less black.
In what varieties is titanium dioxide produced? What makes these varieties different?
Titanium dioxide is produced as anatase and rutile. Rutile has a more stable crystal lattice than anatase. The latter therefore chalks when exposed to the elements outdoors. So it can only be used indoors. Rutile also has a higher hiding power than anatase.
How can you recognize, is the white pigment titanium dioxide?
Titanium dioxide dissolves only in concentrated sulfuric acid. After boiling in concentrated sulfuric acid and then cooling, the solution turns orange, if we add a few drops of hydrogen peroxide. Be careful when adding hydrogen peroxide!
What is the difference between titanium white and titanium dioxide?
Titanium white is a mixture of titanium dioxide and thinners.
How can lead white be distinguished from other white pigments?
Lead white dissolves completely in dilute nitric acid. After adding hydrogen sulphide or sodium sulphide, lead white turns black-brown.