The works of the highly experienced and famous chymist, John Rudolph Glauber

by Johann Rudolf Glauber

Let a piece of the prepared earth be applyed with your hands to the mould, which you must hold in one hand, applying and fitting the earth thereto with the other, or hold it with your legs, that the earth may be applyed with both your hands. Also you must first rub the mould very well with clean sifted sand, for else the earth will so stick to the wooden mould, that a crucible can scarce be taken off without danger, which being done, it is further fitted by striking it with a wooden instrument smoothed for the purpose, by which means the crucible lyes very exactly upon the mould, for by this means crucibles are made very strong; which being done also let the crucible be taken off, and set upon a board, and be dryed, first in the air, then by the heat of the fire, or sun, and then be burned in the first chamber of our fourth furnace, or in a potters furnace. And if you intend only to melt metals and not salts, you need not burn the crucibles if they be well, and exactly made.

Now this caution is to be observed in melting by the help of crucibles not burnt, that you must give fire above by little and little, for fear of breaking the crucibles feeling a suddain heat.

Now that they may be made equal in strength, weight, and thickness, you must weigh one crucible rightly made by the help of the mould in one scale, and a piece of the prepared earth, which is to be put into the other scale, and if they be equal in weight, take out that piece, and put in another; and this do so often, till you be come to the number of the crucibles which you would have made: By this means they are made equal, and you need not cut off any overplus of the earth when it is fitted to the mould, because all are made equal, by reason of the equal weight of the matter of each of them, and the work is sooner done then otherwise.

This indeed is the best way but tedious and laborious, wherefore considering the matter a little more seriously, I found at last that the following way is far better than the former: whereby not only stronger crucibles are made, but also more in one hour, then in that former common way in three or four. Where first, the mould is made of latten (on which I advise you to apply the earth) signified by the letter A. viz. that being the best, which is made by the help of fusion. Then the counter-mould answering this, signified by the letter B. yet so that that do not enter too deep into this, not touching the bottom by the distance at least of one fingers breadth; but in greater crucibles a greater thickness of the bottom is required, as the practise will teach thee.

Let him therefore that is making crucibles apply the earth to the mould, as hath been above said in the First manner, which being done, let him again take off the crucible that is formed or cast, and set it in the air to be dryed. Then having First made a sufficient number of crucibles, let him make the mould clean from the earth or sand, and annoynt it with grease, or oyl Olive taken up with a sponge, as also the counter-mould, into which let him put the crucible being half made and dryed, and into this the mould, which he must strike above twice or twice or thrice with a heavy wooden mallet, that the earth may be rightly, and exactly applyed to the mould; which being done let him take off the mould, and turn the countermould together with the crucible, which let him knock a little against the form (where the crucibles are made) and let him take in his hand the crucible falling from thence; which he must afterwards dry and burn, as hath been above said in the First manner. And by this way are made the best, and the best proportioned crucibles, Fixed and smooth, not only for melting of metals, but also for minerals and salts; the like to which I never yet saw, as being without all danger, if so be rightly made of the best earth. And that they may be made equal in weight and strength, they must be weighed as before hath been said, And this labour is easie and pleasant, when they are made with ones own hand, and that greater or lesser at pleasure.

After the same manner also are made tests viz. by the help of the like kind of moulds, which must not be long but plain like shells as appears by the annexed Figure, A. and B. Not only tests but also cuples are made by the help of these moulds. [See the fifth and sixth Figures.]

Now tests are made more easily this way then crucibles, because the earth only is weighed, and being handled with the hands is put into the counter-mould, which then you must with the upper-part press hard; that it may be made conformable to the mould, viz. plain, not long, that which may easily therefore be made; and for this cause those crucibles are easily again taken out, viz. if the mould be turned, or the counter-mould be a little knocked against the sides of the form. And if the earth be beaten in too fast that it goes out at the sides, you must cut it off with a knife, or else the crucible, or test is hardly taken out, sticking to the brims, which practise will teach thee. For all things cannot be so accurately demonstrated by a pen.

And take this for a caution, that thou do not make thy tests and crucibles of earth that is too soft, but of that which is half dry, otherwise they are hardly taken out of the moulds; for that is more easily and rightly applyed to the mould. And if thou proceed rightly according to the prescript, scarce one crucible of a hundred will be lost.

This also is to be observed, that the superfluous earth which is cut off must not be mixed again with the mass for crucibles, because it is spoyled with the fat, or oyl that is smeared over the moulds, and therefore cannot be so well mixed again, and being burnt cleaves, for which cause bad crucibles are made. Wherefore it is to be kept apart for mending of furnaces that are spoiled with an extraordinary heat of the Fire; or for covers of crucibles that are to be made by the help of the hands only, or of moulds, which we cannot want, if we would work all things exactly.

Now for tyles, and other vessels that serve for distillation, and melting, they are made by the help of wooden moulds after this manner. Let the mould be made exactly like to the tyles, and other vessels, then cut off leaves from the earth being very well prepared, with a copper wier upon two equal tables of wood, and then a piece of the earth is to be laid with a knife upon the mould, that it may there get some hardness; which afterward is to be taken away, dryed well, and burnt. And if any thing further is to be done, viz. by cutting off, or adding, it must be done by earth half dryed, or a little hardened. For by this means any one may get for himself earthen vessels that are necessary, without much cost or pains for certainty sake. For those that are sold, are negligently made, in which oftentimes in the drying, the cracks which are made, are filled up with some earthen liniment, before they are burnt, which therefore are not durable in the fire, but are broken, and that oftentimes not without great loss of the metal, which is again to be gathered out of the ashes by the help of a tedious washing. It is better therefore to work those vessels with ones own hand for certainty sake. For not all and every crucible can alwaies and every where be made equal, and be of a like durableness in the Fire, though they are made most diligently: and therefore a consideration being had of their goodness, they may be used for divers uses, and the better may be used in the melting of the better metals. But let no man perswade himself that all these can indifferently hold in the Fire, although they be the best of all, how many soever you make; for I never yet saw any earth which could hold litharge in the Fire and salt of Tartar, because the best that ever I saw is not free from penetration of them, which is the greatest impediment of some profitable operations, which therefore are omitted.