Melts, Apertures and Height Effects

The effects on the pattern of melts are a combination of several factors. The normal pattern is of spirals as a thread of glass moves down to the shelf and begins to spiral just as any other viscous fluid around the high spot of the drip.  The specific effects centre around three main elements.

Aperture size

The size of the holes determines the diameter of the thread of flowing glass.  Also, the larger the diameter, the quicker the flow.

relatively small apertures

large, long apertures

Height from shelf

The height from the shelf has the effect of determining both the thickness of the thread at touch down and the degree of spiralling.

Relatively low screen

Relatively high screen

Heat

The temperature and time determine the heat work.  The amount of heat (as well as top temperature) influence the flow of the glass.

These three elements interact

Aperture

Aperture size determines the maximum diameter of the thread.  You can thin the threads by having smaller grids or holes. 

The height affects two things. 

Height affects the relative thickness of the flowing thread. Higher makes for thinner strands. The reduction in size can be lessened by placing the apertures closer to the shelf.

Height also affects how the thread behaves on touching the shelf.  More spiralling occurs with height.  A low height will reduce the spiralling to just moving outwards.

Note that when talking about height, it is relative to the aperture sizes.

Heat affects how the glass flows

The higher the heat or the greater the heat work, the faster the glass flows.  Lower heat gives slow moving threads.  Faster flowing glass promotes thicker threads.  Slower moving threads can take up patterns other than spirals.

These factors give you three interacting elements

You could have, for example, a high screen with large openings and low heat to give thin threads with eccentric spiralling.

You could have low height with small apertures and high heat to give thick threads with minimum spiralling.

In theory, you could have at least twelve main combinations by using the extremes of each element, with multiple variations of dimensions in each case.

Experimentation Required

This is to illustrate the interactions are complex and require significant experimentation to be able to predict the probable outcome.  The outcomes will always be only probable, even though you can come to control more aspects of the process and you develop experience.