gloss
The shiny quality of a surface. The surface gloss of an object may change if varnishes or other coatings become tarnished, softened, solubilised or cracked.
friable
Some materials used to create works of art, such as pastels and charcoal, contain very little binding agent. Friable media can separate from their support through friction or abrasion, or may easily crumble into a powdery form. Wood damaged by dry rot may also have a friable surface.
frass
The dust-like debris or excrement left behind by wood-eating larvae and borers.
fracture
A crack or break in a hard material, such as stone, ceramic or bone. Often used to describe a much finer break than a “crack”.
foxing
Localised discolouration of paper, usually appearing as random rust-coloured spots. Caused by both mould growth or metal impurities within the paper and exacerbated by high humidity, dampness and airborne acids.
fold
Where a sheet material (e.g. paper) has been intentionally bent over on itself, often causing the fibres of the material to break or become damaged and hence more susceptible to further deterioration. For example, a folded piece of paper may eventually tear along fold marks.
flaking
Where extreme cracking causes small, thin pieces of varnish, paint or other layers to become completely detached from the main support material.
fill
Where a small piece has been added to an object to replace a missing piece. Fills may be coloured and textured to blend in with the original surface.
ferrotyping
Where two smooth surfaces, one being plastic, come into contact under pressure, causing a shiny surface to be imparted to the non-plastic material.
fading
Loss of brightness or intensity of a colour, usually due to the action of light but may also be due to pollutants and other chemical interactions.