Modern Spread Cuts

(via Diamond Cuts in Historic Jewelry:1381-1910) Herbert Tillander writes:

The old Spread Cut Brilliants were the successors of the early Mirror Cuts and, like these, were inspired by the demands of fashion. If good proportions were possible, then of course the diamond would not be spread. But otherwise, depending on the irregularity of the rough, the final result might by anything from an overspread Brilliant to a mere trinket. Today most Brilliant Cut diamonds are Spread Cut, emphasizing brilliance at the expense of fire. Since they are produced commercially, the saving of weight is of major importance, even though this means that the light effects are considerably reduced, and despite the fact that a well-proportioned stone can be worth far more than a Spread Cut one, not to mention Fish-Eye.

Basil Watermeyer gives a splendid example of a Spread Cut. He states that such a diamond ‘will produce an equal flow of reflected light through table and crown facets.’ This total balance of light reflection can fool the eye into believing that the stone has life. When these proportions are used it is stressed that the stone is very sensitive to any change in the base angle of 41°. A 40¾° base angle will immediately produce a Fish-Eye and a 41¼° angle will produce a dull ‘inner circle.’

Another equally Spread Brilliant Cut was proposed by Parker in 1951. These figures conform with a crown angle of 25.5° and a pavilion angle of 40.9°. Oldendorff believed that Paker Cut might be quite attractive but ‘somewhat lax.’

Parker’s Spread Cut
Table size: 66.1%
Crown height: 8.1% - Angles: 25.5°
Pavilion depth: 43.35% - 40.9°

Watermeyer’s Spread Cut
Table size: 66.66%
Crown height: 11.5% - Angles: 33 - 34°
Pavilion depth: 43.5% - 41°