Rosin is brittle and friable, with a faint piney odor. It is typically a glassy solid, though some rosins will form crystals, especially when brought into solution. Rosin mainly consists of different resin acids, especially abietic acid with general formula of C₂₀H₃₀O₂ . 

Solubility

Insoluble in water; freely soluble in alcohol, benzene, ether, chloroform, glacial acetic acid, oils, carbon disulfide, dilute solutions of fixed alkali hydroxides. Low toxicity. Hard and friable at room temperature; soft and very sticky when warm. Combustible.

Chief constituents: Resin acids of the abietic and pimaric types, having the general formula of C₂₀H₃₀O₂ , and having phenanthrene nucleus.

Melting and Flammability

The practical melting point varies with different specimens, some being semi-fluid at the temperature of boiling water, others melting at 100°C to 150°C. It is very flammable (Flashpoint 187ºC), burning with a smoky flame, so care should be taken when melting it.

Rosin Salts:

Rosin combines with caustic alkalis to form salts (rosinates or pinates) that are known as rosin soaps.

Miscibility and compatibility

Natural Gum Rosin or Pine rosin is compatible and miscible with many different chemicals and oils including the following:

• Mineral Oils and Waxes (Paraffin)
• Candelilla
• Bees Wax
• Carnauba Wax
• Lard
• Stearic Acid
• Coconut Oil
• camphor
• turpentine
• Linseed Oil
• eucalyptus essential oil
• Vitamin E
• cocoa butter
• Sweet Almond Oil
• Olive Oil
• Palm Oil
• Caster Oil
• Sunflower Oil
• Canola Oil
• Dammar Gum (or Dammar Varnish)
• shellac
• Methanol (Methyl Alcohol)
• Ethanol (Ethyl Alcohol)
• Titanium Dioxide
• Talcum Powder
• Calcium Carbonate
• Corn Starch
• Many other alcohols and vegetable oils are also miscible with rosin.