428 



AMERICAN HOMES AND GARDEN? 



November, 1910 



HANDICRAFTSMAN 



Conducted by A. Russell Bond 



Home-made Pottery 



By W. P. Jervis 



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T may sound paradoxical, but the first point 

 for the novice in the art of forming ves- 

 sels of clay to consider is the last stage 

 of the process. In other words it is nec- 

 essary to know at what heat the clay you 

 propose to use will mature in the firing. 

 This is the definite point which has always 

 to be kept in view, both in the mixing of clays and glazes. 

 There are several ways of acquiring this knowledge, (a) 

 by purchasing clay from a pottery, (b) by adopting a for- 

 mula or mixture the maturing point of which is given, and 

 (c) by empirical trials. 



We will presume you have access to a natural red or 

 buff clay and want to find what degree of heat is necessary 

 to convert it into serviceable pottery. Take some of this, 

 dry it well and then pound it as fine as you like, picking 

 out the stones and any other foreign substance it may con- 

 tain. Scatter this into a pail of water, a handful at a time, 

 until there is sufficient to make a fairly thick liquid. Stir 

 this well until it attains a certain smoothness. But it will 

 not be free from grit and it is necessary 

 to pass it through a lawn of about 80 to 

 100 meshes to the inch. Take another 

 pail, and taking a small quantity of slip 

 at a time, pour it in the lawn and by either 

 tapping it on the side, or using a sponge 

 and keeping it in motion with the 

 hand, the slip is freed from its impurities. 

 Lard or butter tubs, obtainable from any 

 grocer for a few cents, make excellent 

 slip tubs. Let this slip stand a few hours. 

 The clay particles will sink to the bottom, 

 leaving clear water on the top. Pour off this water, stir 

 the remainder well, place some of it on a plaster bat 

 and you will soon have plastic clay. Before using this 

 clay it must be "wedged," 

 that is, kneaded together 

 into a perfectly homoge- 

 neous mass, free from air 

 bubbles. Take as much 

 clay as you can conveni- 

 ently handle; with a thin 

 brass wire cut it in two, and 

 then extending your arms, 

 bring the two portions 

 sharply together, repeating 

 as often as necessary; or 

 you can bring the mass 

 down sharply and repeat- 

 edly on a stone or brick 

 floor, cutting it with the 

 wire as before. Clay can- 

 not be wedged too thor- 

 oughly, so do not grudge 

 the expenditure of a little time. The result should be a 

 plastic mass which cuts cleanly without showing any holes 

 or joints. Make a small slab, say 2x3 Inches or 3x4 

 inches, of this clay, and carefully mark it out into ten 



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parts. This can be done with the edge of a rule. It makes 

 it more exact if the slab is made a little larger, marked out 

 as shown in the accompanying drawing, and when about 

 as hard as leather, trimmed with a knife. The hatched 

 parts show the parts to cut away. If the clay is too plastic 

 it will take a long time to dry and possibly go out of shape. 

 Whilst extreme plasticity is a good feature in a modeling 

 clay, a potters clay should be much "shorter," for it will 

 then dry quickly and retain its shape. The best shortener 

 is sand. Clay can be kept in condition by placing in a 

 cool place and covering with a damp cloth. These natural 

 clays mature at from 1030 to 1130 centigrade. Try 

 it at 1070 (cone 04), and when it is fired touch it 

 with the tongue and if it has not had sufficient fire it 

 will adhere slightly to it. If it shows signs of vitrification 

 and is dark and glassy it is overfired. I use a red clay 

 which will not retain its shape at 1130 (cone 01), 

 and to correct this I add 10 per cent, flint and 5 per cent, 

 china clay, and this is the standard I shall use in these 

 lessons. The flint renders the clay harder, but it also in- 

 creases the shrinkage, this being about 

 one-eighth from the mold to the fired 

 ware. The china clay improves the color. 

 So a slab made as above instead of meas- 

 uring 2x3 or 3x4 is one-eighth less. This 

 shrinkage is caused by the particles of clay 

 being brought closer together during the 

 firing and you cannot work without know- 

 ing what it is. When the clay is fired it 

 is known as biscuit. A good hard biscuit 

 is desirable, but it sometimes happens that 

 the ware is short fired and the biscuit is 

 soft, and this will be dealt with later. 



I have spoken of plaster bats. Plaster is a most impor- 

 tant article to the potter and a number of these bats are 



indispensable. They may 

 either be round or square. 

 To make the latter take a 

 square of hard wood or 

 thick glass of the size re- 

 quired and make a frame 

 of wood or very strong 

 cardboard, binding it firmly 

 together with cord. A lit- 

 tle clay at the joints will 

 make it tight. A round 

 one can be made in an 

 agate or iron frying pan or 

 pie plate. Measure how 

 much water it takes to fill 

 these to the required thick- 

 ness, about %-inch. Put 



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Testing slab of clay 



Rolling a coil of clay 



this same quantity of water 

 in a bowl or wide-mouthed 

 pitcher and add to it one pound of dry dental plaster to 

 each pint of water. Let this stand for about four or five 

 minutes and in the meantime with a cloth or sponge soap 

 all the inside parts of the mold, rubbing it well in so that. 



