t 272 3 



%UY. Desciiplion of an improved Glaze for Porcelain. By 

 Mr. John Rose, c/" Coal port, Shropshire*. 

 -jj Coalpoit, March 24, 1820. 



Sir, — j1a\ ING for some tim.e made use of a glaze for porce- 

 lain, which gives me great satisfaction, and into the composition 

 of which neither lead nor arsenic is admitted, I beg leave to 

 submit the same to the consideration of the Society of Arts, &c. 



The common glaze for porcelain and the finer kinds of earthen- 

 ware contains a considerable ])roportion of glass of lead ; this 

 ingredient however, on account of its being mixed with a certain 

 proportion of siliceous earth and other vitrifiable materials, unites 

 with them ijito a glass, which, although easily fusible, is not in 

 the least corioded or acted on by any articles of food. It is not, 

 therefore, from the apprehension of any injury to the health of 

 those who use vessels of porcelain, that the use of lead in the glaze 

 is objectionable, but because it is extremely liable to combine 

 v.'ith and degrade the more delicate colours, especially those 

 given by prrparations of chrome and of gold. This is particu- 

 larly the case in the more expensive and elaborate products which, 

 &« account of the multiplicity of their colours, require to be re- 

 peatedly heated, or Jired. I trust, therefore, that the Society 

 will consider the communication of a receipt for glazing, in which 

 the abovementioned defects are avoided, as worthy of their fa- 

 vourable notice. 



The principal ingredient of my glaze is felspar, of a somewhat 

 compact texture, and a pale flesh red colour, which forms veins in 

 & slaty rock adjoining to the town of Welsh Pool in Montgomery- 

 shire. This material, being freed from all adhering pieces of 

 slate and of (juartz, is ground to a fine povvder, and being thus 

 prepared, I mix with 27 parts of felspar, 18 of borax, 4 of Lynci 

 sand, 3 of nitre, 3 of soda, and 3 of Cornwall China clay. This 

 mixture is to be melted to a frit, and is then to be ground to a 

 fine powder, .3 parts of calcined borax being added previously to 

 tlie grinding. 



The specimens accompanying this IjBtter, are, 



1. The felspar in its rough state. 



2. Do. ground to a fine powder. 



3. Some of the glaze ready prepared for dipping. 



4. Specimens of porcelain glazed. 



5. Do. both glazed and afterwards painted^ in order txj 

 eliow the solidj-ty and biilliancy of tlie colours when used on this 

 ^laze. I am, sir, &c. 



A. Aikin, Esq., Sec. &c. John Kose. 



• From the Transactions of the Snciefy for the Encottragcment of Arts, 

 Mfimifactnres, and Commerce, for 1820. 'i'he Isis gold niedul of the Society 

 iA'as voted to AJr. Rose for this comimu)ication. 



§onie 



