Solvents

As solvents for resins, such liquids are used that volatilize as quickly and completely as possible or dry into hard films.
Solvents are liquid organic compounds that are capable of dissolving other, especially solid, organic products.
Each solvent has a peculiar effect on the varnish prepared on it.
They differ in origin as well as in their distinct chemical composition.
The oldest solvents for resins are oils (linseed oil and walnut oil). Copal and amber were dissolved in them.
For the production of oil varnishes, bleached crude or polymerized oil is used.
Depending on the oil used, different varnishes are obtained:

1. Varnishes on quick-drying oil (tung oil).
2. Varnishes on drying oils.
3. Varnishes on semi-drying oils.

Of great importance for the ability and film-forming properties of the varnish is the prior treatment of the oil.
Depending on the oil content of varnishes, we divide them into:

1. Oily, with maximum oil content.
2. Medium-fat, with a medium amount of oil.
3. Lean, with a minimum amount of oil.

Oily varnishes

Due to their high oil content, they are very flexible and resistant to weathering. However, they are characterized by less hardness.

Medium-fat varnishes

They give hard films that are resistant to weathering.

Lean varnishes

They contain the maximum amount of resin and are most similar to pure resin varnishes.
They dry with the greatest ease and speed.
With hard resins they give films that are hard but brittle. Hardly resistant to weathering.
As coating varnishes rather not used, as they are difficult to remove and darken.
In addition to oils, resins dissolve in:

• vegetable volatile oils at ordinary or elevated temperatures (lavender, spikenard, rosemary and clove oils);
• mineral volatile oils: petrol, petroleum ether, acetone, chloroform, camphor, spirit, and in aromatic hydrocarbons derived from gas tar - toluene and benzene;
• balsamic turpentine.

Oil, spirit and turpentine varnishes are used to remove tarnish, to thin or thin paint and to cover the surface of a finished painting, and as an additive to painting.