With these latter glasses there is, of course, considerable risk that the partial fusion and consequent contraction of the fireclay of the crucible may result in its destruction and the entire loss of the glass.
Into the square axial hole fits the square end of a hooked iron bar which projects several yards beyond the mouth of the furnace; by means of this bar a workman moves the fireclay cylinder about in the glass with a steady circular sweep.
The doorway is closed by two fireclay blocks at E.
A, A, A, playing on work laid on thefireclay slab B, thence passing under this and out through the elbow-pipe C.
This passes into the furnace through the two holes, C, C, and plays under and up around the muffle D, standing on a fireclay slab.
But heat the coal in an enclosed vessel, say a big fireclay retort, and it cannot burn up because the oxygen of the air cannot get to it.
To the end of the fireclay cylinder a long, detachable iron handle is fixed so that the man who undertakes the stirring may stand at a distance from the hot furnace.
The stirring is carried out by means of a cylinder of fireclay which is first of all heated to the temperature of the molten glass before it is introduced.
Large pieces of glass are heated till they are just soft, then they are passed into iron or fireclay moulds designed so that the glass is formed into discs or slabs suitable for grinding by opticians.
During the final stages the operation is hard labour indeed and, finally, it is not possible to stir any more, then the fireclay cylinder is either removed or left in the glass.
It is constructed wholly of fireclay--fireclay bricks, quarries, and cement.
Every single joint must be perfectly made withfireclay cement or paste.
I have given the plan, elevation, and sections of a fireclay heating apparatus.
Absolutely faultless workmanship must be employed throughout, and the fireclay materials must be literally of the very best and soundest description.
Rapidly heated fireclay is seldom so resistant to heat under commercial conditions as that which has been more steadily fired.
For this reason it is customary to mix fireclays with a large proportion of non-plastic material of a somewhat coarse texture, the substance most generally employed beingfireclay which has been previously burned and then crushed.
Some shales, when finely ground, make excellent clays for architectural terra-cotta, portions of all the better known fireclay deposits being used for this purpose.
The most important characteristics of a fireclay are that it shall be able to resist any temperature to which it may be exposed and that the articles into which it is made shall not be affected by rapid changes in temperature.
On the Continent, and to a much smaller extent in Great Britain, refractory articles are made from mixtures of grog or burned fireclay with just sufficient raw clay to form a mass of the required strength.
For this purpose a mixture of fireclaywith finely powdered felspar or Cornish stone is used.
This material is known as grog or chamotte and has the advantage over other substances of not affecting the composition of the fireclay to which it is added, whilst greatly increasing its technical usefulness.
Several grades of fireclay have long been recognized on the Continent and in the United States of America, but the recent Specification of the Institution of Gas Engineers is the only official recognition in Great Britain of definite grades.
For those purposes it is necessary that a fireclay should possess high infusibility (p.
Both these clays may be equally refractory, but the underclays are those to which the term fireclay is usually applied.
Very few fireclays meet all these requirements, and it is usual to mix a certain proportion of ground firebrick, ganister, sand or clay with the fireclay before making up.
There is no fixed standard of refractoriness for these clays, but no clay should be classed as a fireclay which has a fusion point below 1600 deg.
For special purposes special mixtures are required and many expedients are used to obtain fireclay goods having certain specific qualities.
The South Staffordshire fireclay is worked principally in the neighbourhood of Brettle Lane and Stourbridge, and is employed in the production of firebricks, gas retorts, pottery, etc.
The principal minerals worked within the limits of the South Staffordshire Coalfield are coal, ironstone, and fireclay from the Carboniferous formations, and limestone from the underlying Silurian rocks.
Their ends are connected at the top to two conductors, which pass down inside the tube and end in a fireclay plug at the bottom.
This tube projects from the fireclay casing into the medium to be examined, and can be pushed in or out as required.
A temperature that will make steel run like water and melt down fireclayhas absolutely no effect upon it.
The principle is applied in the following manner: A cylinder of fireclay slides in a metal tube, and has two platinum wires one one-hundredth of an inch in diameter wound round it in separate grooves.
The wires of the couple should be insulated from each other by fireclay leads or tubes, and it is well to encase them in a fireclay, porcelain, or quartz tube to keep out the furnace gases, which in time destroy the hot junction.
As this compound comes from the carburizing pots it contains bits of fireclay which represent a part of the luting used for sealing, and there may be small parts of work or bits of fused material in it as well.
This fits in a bell on the end of the cast-iron pipe B, which is luted in position with fireclay before the packing begins.
Fireclay and common putty seem to be favored by many.
After packing the work carefully in the boxes the lids are sealed or luted withfireclay to keep out any gases from the fire.
The screw threads should be filled with fireclay (as recommended by Faraday) before the joint is screwed up.
Of course some control may be exercised by "soiling" with fireclay or using an oxidising flame; but the erratic behaviour of spelter in this respect is the greatest drawback to its use in apparatus construction.
A good protection is a layer of fireclay laid upon the more delicate parts, such for instance as any screwed part.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "fireclay" in a variety of sentences. We hope that you will now be able to make sentences using this word.
