Manufacturer and builder 3, 1872
[294] Waterproof and Fireproof Paint Without Oil.
On page 159, Vol. III., you give a new process for making paint without oil; but you do not give the proportions of the oxide and chloride of zinc, nor of the starch used. Please give these particulars; and as the zinc-white is sold by weight, and the chloride is a fluid sold by measure, please state whether the proportions are to be determined by measurement or absolute weight. Also, if the starch ought to be dissolved, or to be added dry to the zinc mixture? Would it do to color it with a pigment that had been ground in oil? Must it be used immediately, or can it be kept from hardening by protecting it from the action of the air, by keeping it covered up? - T. S. C., of Shelbina, Missouri.
Our correspondent asks more than is necessary. We have made the compound in question without troubling ourselves about the proportions, only using judgment in the employ of the quantities while mixing. In regard to the question if the starch is to be dissolved, our recipe commences with saying, "Boiled starch may be made waterproof," etc. As to the question of mixing it with a pigment ground in oil, we said, "A mineral pigment may be added," which does not mean a pigment ground in oil. Our correspondent surely knows that water and oil don't mix, neither does a watery mixture and an oil paint. As we have said that it becomes hard "in fifteen minutes, by the formation of oxychloride of zinc," it is evident that it does not become bard by drying in the air, and that covering it up will not make it keep. We will, however, give some practical information in regard to the preparation; take the liquid chloride of zinc and rub in it so much zinc-white as to give it the same consistency of a white paint; do this on a stone in the same way as paints are rubbed up to a homogenous mass, without granules. then boil your starch in the usual way, without that you need to weigh the proportions of dry starch and water; add to the boiling starch gradually the mixture of chloride and oxide of zinx, till you have put in enough to make it so opawue as to cover the objects you are goint to paint to about the same degree as zinc-white ground in oil would cover them. Then add your dry mineral powder, red-lead, ochre, mars-red, chrome-yellow, or green, etc. It has to be observed, however, that while in mixtures of paints ground in oil, the oil enveloping and protecting the mineral materials prevents chemical reactions or changes of the colors used, this protection does not take place in watery mixtures, and that the color of some mixtures may become considerably changed and even destroyed, when used injudiciously. Orpiment, for instance, is very unstable when mixed in water colors.
[303] Making Black Paint from Molasses.
There is a party here who manufactures from the most inferior kinds of molasses a beautiful black paint, of much deeper color than lamp-black or ivory-black. I wish to inquire if this process is patented here, or a secret unknown elsewhere. Please oblige "A Subsrciber", New-Orleans, La.
The process is not patented here as far as we can ascertain, while, besides, it is no secret at all. It was described under the name of Waltl's method, in the Polytechnische Central Halle, for 1859, and consists simply in carbonizing the sirup with strong sulphuric acid in place of heat. Sulphuric acid has so much affinity for water, that when placed in contact with any carbohydrate, as wood, sugar, etc., it will compel the hydrogen in the substance to combine with its oxygen so as to form water, which is imperiously demanded to satisfy the desire of the sulphuric acid; this will go on till all the hydrogen is combined with all the oxygen, and as in sugar and molasses these two elements are present exactly in relative quantities sufficient to form water, the pure carbon will be left begind. The process consists in heating strong sulphuric acid in a porcelain or well-glazed earthenware vessel; a cast-iron pot may also be used, provided it is first cleaned from rust by means of diluted sulphuric acid; in this heated strong sulphuric acid, the molasses is gradually poured under sonstant stirring; as the acid will combine with many atoms of wter, less sulphuric acid is required than the theory of the simple atomic weights would seem to indicate. When the black mass becomes thick, it is left to cool, and then repeatedly washed with water, and afterward dried. In order to perform this process economically, it is necessary to make provisions to dispose at a profit or the diluted acid proceeding from the washings of the carbon black obtained, either to a dyeing establishment, or for telegraph batteries, or to add to the manufacture of black paint that of one of the many chemical compounds for the formation of which diluted sulphuric acid is required.
Ei kommentteja :
Lähetä kommentti