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schema:abstract "8 - A Way to Make Ordinary Frit with Polverino, Rocchetta, and Spanish BarillaFrit is nothing other than a calcination of the materials that make up glass, and although one could melt them without calcination, and would make glass, this would only succeed after a protracted period of time and a large amount of grief. Consequently, the calcination process was developed to make and to calcine frit in an oven called a frit kiln. When it is well calcined and the doses of the materials are right, and conform to the quality of the barilla [soda), it fuses readily in crucibles and it clarifies marvellously. Frit that is made of polverino will make white glass, but it will be ordinary glass, the frit made of rocchetta, also from the Levant, makes a more attractive glass called crystallino. Barilla of Spain is richer than the polverino for ordinary glass; nevertheless, it does not make the glass quite as white and beautiful as that of the Levant because it always tends to have a bluish cast.So in order to make it [polverino frit], sift the polverino through a fine sieve. Crush the small pieces that do not pass through in mortars of stone and not of metal, so that it will not take on any colour. Do the same thing for the rocchetta and barilla, but do each one by itself, and continue to work them until they are well ground and sifted in a fine sieve. As the common proverb of the art of glassmaking says: a fine sieve and dry wood bring honour to the furnace. Then with any of these sodas, 100 pounds of soda ordinarily requires 85 to 90 pounds of tarso, for example. As previously described in making crystal, this should be finely ground in stone mortars only, and not in any other kind. Then pass it through a fine sieve using more or less depending on the quality of the soda and its richness. You must always perform an assay of how much to put in, as is well known in the art.Now sand, and especially that of Tuscany, which is found in the Arno River valley is much richer and has much more salt already in it than tarso. So never add more than 6 to 8 pounds [salt] per 100 [tarso]. Before it can be used, this sand must be well washed of all its extraneous sediment and sifted. lt will then make a nice white glass, but tarso always makes the most beautiful of any sand found in Tuscany. Procure the required dose of the sand or tarso as described above, first mix it together and incorporate it very well with the soda or well-sifted polverino. Then put it in a hat frit kiln and spread it well. Begin mixing it and blending it with the rake in the kiln, so it calcines well. Continue for 5 hours, always maintaining the fire, until it begins to form lumps and grow into little pieces, like nuts. When the fire has been maintained as described, and the frit has been well worked with the rake for the indicated space of 5 hours, the frit will be prepared in full perfection. If you want to see if it is well made then take a little out. As it cools if it lightens to a yellowish white, then it is finished. However, calcining it more than 5 hours is not bad, because the longer it is worked the better it is calcined, and the quicker it fuses in the crucible. Being in the frit kiln a little Ionger consumes and purges the yellowishness and scum that it has within it and the glass becomes cleaner and purer. Remove the frit from the kiln when it is hot and glowing, pour 3 or 4 buckets of fresh water over it then put it in the cellar in a damp, cool place.Take the leftover sludge from making salt, as previously described [chapters 1, 3], and put it in the same pans used for the polverino lye. Pour common water over it, and position basins under the pans so that they receive the water, which little by little drips through the residual sludge, and becomes a much stronger lye. Store this pure and clear lye separately and every now and then, sprinkle it over the frit. When the frit is piled up in a moist place and sprinkled with the lye for the space of 2 or 3 months or more, the Ionger the better, it will solidify together like rock such that you must break it up with a pickaxe. Now when it is in the crucible it will melt wonderfully in a short time and make the whitest glass; almost like crystal. This effect is caused by the lye, which leaves behind its salt. When lye is not available, sprinkle it with common water. Even if it does not have as great an effect as the lye, it nevertheless does work well, and it helps a lot to facilitate fusion. Therefore frit should always sit for some months, which when made this way always requires less firewood to be consumed, and makes the glass smooth and pliable to work." ;
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schema:description "Modo di fare Ia fritta ordinaria, cioè di Polverino, di Rocchetta, e di soda di Spagna. Cap. VIII., L´arte vetraria distinta in sette libri del R.P. Antonio Neri Fiorentino: ne quali si scoprono, effetti maravigliosi; & s´insegnano segreti bellissimi, del vetro nel fuoco & altre cose curiose." ;
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