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Shear Marks

Shears were used to cut off the gob of molten (elastic) glass as it was being dropped into the mould ready to be pressed - see picture top left below. Although this is modern production at Fenton, the technique, or the tools have not changed since the early days of  pressed glass.

Because the blades of the shears were relatively cool, the act of cutting the very hot glass (about 1900 degrees Fahrenheit at this point) resulted in a fractional cooling and resultant hardening of the surface of the glass at the point where it was cut. This is the shear mark - also sometimes misleadingly called the sttraw mark.

Skilled glassmakers had several techniques to get rid of this mark:

- they could “flip” the gob of glass as it was being dropped into the mould so the cut edge was not in a prominent position.

 

- they could hide the shear mark in the intricacies of the pattern, but if the design had large plain areas then the shear mark is more easily seen, as in the pictures below. The iridescent surface of Carnival Glass will also often emphasize the appearance of a shear mark.


- the glass item could also be re-heated and the shear mark smoothed or “fire-polished” out.

As well as skill, this could also take more time than might have been available under the pressure to maintain production volumes!

The other photos below show a shear mark on a Fenton Pine Cone plate, from a series of different angles. As  this pattern has a large plain area in its center, the shear mark is clearly visible. It is not a flaw or damage - but is simply a feature of pressed glass.

 

Shears cutting gob of glass

 Fenton Pine Cone plate with shear mark

 Shear mark

Shear mark in detail

glassmaker's shears

 

Here is a diagram of glassmaker's shears. The dome-shape on the handle, sometimes called a "stomper" was introduced in the 1950s. It was used to smooth out the shear mark when the hot glass had been dropped into the mould, immediately before pressing.