Slimes are treated in the Slime Plant

First of all the fine tin slimes are allowed to settle in SETTLING PITS, where the water is drained off and they become thickened. Then the exact amount of water required can be added at a controlled rate. The action of sun, air, wind and the light spray of water on the settling slimes is not fully understood, but they all help to break up the tin particles.


The thickened slimes are raised by means of a dipper wheel to the first ROUND FRAMES. The light waste runs off quickly, leaving the concentrated tin at the top, to be brushed down by a rope brush into a separate launder. Such was the value of tin, this concentrate may be processsed two or three times more to extract the maximum amount.


The Round Frame deck is made from Parana pine; no other wood is as effective and its freedom from knots ensures a smooth surface.The gradient of the deck and the flow of water, which can be regulated by the diamond -shaped buttons along the upper edge, help to determine the quality of the concentrate.

The final concentration is done by HOLMAN SLIME TABLES. These are very slightly different from the Sand Tables, though an untrained eye would hardly notice; but the tilt, speed and water flow all influence the final quality.

At various stages in the dressing process, quality checks are carried out. This is done by VANNING: a small amount of the concentrate is put on a large vanning shovel and is then swirled round with clear water in a circular motion. A skilled vanner will soon see a line of the grey tin particles thrown up along the upper edge of the shovel and will be able to make an accurate estimate of the percentage of tin present. He can then make any slight adjustments to the machinery which may be necessary - for example, he might alter the tilt of one of the tables.


The final stage at Tolgus, a chemical check, or ASSAY, was done.

Assay Lab

You often saw a white-coated figure in the Assay laboratory, absorbed with test tubes, their contents changing colour as if by magic.

The final assay should have corresponded closely with the one done at the smelters, for the price they paid for the tin was based on the percentage of pure tin in the concentrate

History of Tolgus Stream Tin & Lode Tin Management & Workers 12-headed Cornish Stamp Sulpher & Arsenic Waste Disposal.
Water Power The Sand House The Slime Plant. Assaying. Smelting Trevithick Trust
TOLGUS Tin streaming at Redruth