chapter 3 activity 6 paints. ancient paintings where did they get their paint from?
TRANSCRIPT
Leonardo Da Vinci made some of his own oil paints
Pigment
• finely ground particles or powders that are dispersed in paints, provide color
• produced as insoluble products of double replacement reactions
• May be a variety of colors depending on the metal ions that are involved in the compound
The mixture of cobalt(II) chloride and aluminum chloride is being
homogenized
Heating of the mixture in a test tube
After several minutes the reaction is completed
The finished productCobalt blue pigment
Pigments
Solutions of cadmium(II) nitrate and sodium sulfide
heating the solutions
precipitation reaction
Filtering the precipitateStirring the precipitate
Cadmium yellow pigment
Verdigris pigment[Cu(CH3COO2]2. Cu(OH)2. 5H2O
The reactions that produce an insoluble compound are called DOUBLE REPLACEMENT REACTIONS
Pigments
The reactions that produce an insoluble compound are called
DOUBLE REPLACEMENT REACTIONS AgNO3(aq) + KCl(aq) ‑‑‑‑> AgCl(s) + KNO3(aq)
The product of this reaction that is insoluble in water is called the precipitate (ppt). It is this substance that can be used as the pigment in paints.
Pigments
NO3-precipitate
Binder• A substance that is mixed with the pigment
to bind the pigment particles together• Once the paint is dry, it also binds the
pigment to the painted surface.• Could be
– oil (oil based paints)– acrylic resin (acrylic paints)– Egg yolk (tempera paints)– glue
Solvent• Usually a volatile liquid that is added to the
pigment and binder to adjust the viscosity (resistance to flow) of the paint.
• It evaporates and does not become part of the paint film that remains on the surface.
• Not all paints contain a solvent.
SolventThis is the paint when it is first applied: Pigment and binders are the circles and squares. The blue is the solvent.
The solvent is starting to evaporate. Pigment and binder come closer together.
Paint is dry, pigment and binder have been fused together and form a tough film.