OUR POTTERIES.

Waikato Times, Volume XVI, Issue 1390, 31 May 1881, Page 2

OUR POTTERIES.

The following communication has been received from a valued correspondent, Mr James Wright, of the Hamilton Pottery Works, a gentleman who has had extensive experience in the Staffordshire Potteries, and who has given in Hamilton abundant proofs of his ability to turn out the best class of work : — "The important station which this art holds amongst our manufactures renders every attempt at improvement, worthy of consideration and attention. It has been said ' the m.m who can set one ear of corn to grow where one never grew before, deserves the thanks of his country ;' but what does that man merit who by indefatigable industry contributes materially to the advancement of the interests of his country in the improvement of its manufactories. The following remarks are the result of upwards of eighteen years study and repeated experiment, and no pains have been spared m examining the cLiy of New Zealand. The qualities of china clay differ very much, being always mixed with pai tides of talc and mica, and in analyzing iound to contain 60 percent, of argal, and 20 of sil^x ; consequently they aie infusible at the most intense heat. These days are of a yellowish white colour, smooth and greasy to the touch. I shall make a tew more remarks on the different constituent parts of the clays of Auckland. The constituent parts of these clays in the province of Auckland aie argal and mlicious stones, the proportion of these two mgiedunits to each other is variable, sometimes argal exceeds, but most commonly sihcious ingredients predominate. When argal exceeds in proportion to silex (although this seldom occurs), ratio is as three to one, or two to one, but in some cases it appio.iches nearer to equality. Whf>n the silicious exceeds, which is frequently the case, it ib found at the most m the proportion of four to one and three to one. It very 1 arely approaches to an equality. These pro^oi tions produce different effects The cliy in which the mlioious ingicdienta enter in proportion of three to one are the best for the use of porcelain, those in which asral exceeds are the best for coarse eaitheuware, because lebS acted upon by alk.iheß. That kind of silicious htone w hich constitutes the sandy p.irts of clays, should be attended to particularly. It is frequently found that quartz or felspar and some other species will influence the internarproporitie-i of the clays. The colours th.it occur in clay are numerous ; tho'-e produced by vegetable or bituminous particles aie destroyed by heat in <iv open jtii'P and are by no means pei judicial, but tho>e which aiise from metallic particles are obstinate, and should be avoided as much as possible. With ic>pect to clays which contain •iiirdl and silex only, they will not melt with any heat that can be produced in kilns or ovens in potting, in v/hat-ever pi opor tions they may be mixed together, but caloarious earths in the {proportion of ten to twelve per cent will render any clay fumble. There are few clays but Avhat contain cither more or less calcarious eaith. The oliys for njiiuuf.icturing 1 porcelain should be of the gieatest fineness, also such as do not retain water with too much tenacity, which is the case when argal is not combined with fixed air, thcieforo all clays ought to be exposed to the action of the atmosphere for a long time previous to using. White i» the natuial colour of all earths; other colouis which are found in them piocecd fiom inflammable or metallic substances Calcarious earth in its common state is limestone or &par, magnesia or muriatic earth, which in their pine state are not so easily dissolved as when combined with fixed air. Earth of Argal forms the basis of common alum, and by some called aluminous earth, which in paits is common clay. To distinguish it from other heterogeneous parts, it is called aigal, and is never found pure. The finest part if extracted fiom alum, and not fusible in the strongest heat requiiedfoi china or earthemvaiu. Argal m its usual state of dryness, is capable of absoibing two-and-a-half times its weight of water Silicious earths found m a stony state abound in flint, for which icason they aie called silicious. The piuost are found in crystals and quart/5 of a pure white colour. In the first place I shall give you the component parts of the clays of the Waikato Coal Mines. I received five samples of clays ft om the coal mines. Nos. 3 and 5 are suitable for the finest white pottery. They are of a mUcious and argalicioua quality, and must be of the best for w lute pottery. No. 4, a fine argahcious clay. Nos. 1 and 2, fine led clay for water bottles, wme and butter- coolers in the Mosaic style. These five clays aie for the finebt kind of pottery and for all colouied bodies, red, black, blue, drab, lilac bioun, yellow &c. I have received some ih&t-class samples of clay from Captain Beeres place, suitable for the finest pottery. Of the clay from the Hamilton Pottery, some is of the argalaceous, and some of it sicihous kind, for the coarser kind of earthenware and terra cotta, butter and pieserve jars, milk pans, &c. I have received a fine sample of clay from the vicinity of Hamilton Statiou, and another fine sample from Mr Wood's place, Ohaupo. I have received some good clay from the Drury Coal Mines, but some of them contain little metallic particles which are obstinate, but they are good for the courser kind of pottery. I have a fine sample of clay from Captain Symonds" place, Muddy Creek, Onehunga j it is a fine silicious clay, and well adapted for the superior kind of earthenware pottery. But the finest clay which has come under my notice is a sample from the Whangarei Coal Mines. It is a fine silicious and argalaceous clay, and of the finest quality for china and fine earthenware. A few more remarks on the quality of the clay called marla. Marls are of a loose pliable texture, easily reducible to powder, most readily separating and diffusing in water. When dug out of the earth they are pretty hard, but being exposed to the air, soon fall to dust. There are several sorts of marls, of various colours and qualities denominated by different appellations; the argalaceous marl will be found the best for fine pottery. I shall in a future issue explain to you the various means made use of to prepare the clay for the potter to use, and the minerals made use of in the manufacture of fine pottery. The minerals I have found are of the best quality for the finest pottery.

The municipal elections in Spain are favorable to the supporters of the Ministry.