Memoir on Gluten. II 



varnifh nearly fimilar;' but that obtained by an alcoholic 

 foliation of gluten evaporated to the confidence of fyrup is 

 preferable. 



I employed this varnifh to preferve feveral objects of na- 

 tural hiftory from the influence of damp air. As it pofleffes a 

 certain degree of elafticity, I confider it to be equally proper 

 for varnifhmg anatomical preparations. It is more conve- 

 nient than frefh glue for cementing broken porcelain. 



This firft trial neceflarily conducted to the idea of employ- 

 ing the folution of gluten as an excipient of different colour- 

 ing matters. I mixed then a certain quantity of glutinous 

 varnifh with white oxide of lead, minium, indigo, and car- 

 mine, and obtained colours more or lefs bound, but which 

 were all eafily extended with the pencil, which adhered 

 ftrongly even to glafs, dried fpeedily, and had no difagree- 

 able odour. I remarked that the vegetable colours mixed 

 with greater facility than the oxides. 



As I formed thefe mixtures in mortars of glafs or agate, 

 I did not obtain colours fo homogeneous as if I had ground 

 them on porphyry. When thefe colours are well prepared, 

 that is to fay, when the proportion of the colouring matter 

 does not exceed that of the gluten, the painting may be 

 wafhed without any fear of altering it, unlefs rude friction 

 be employed. 



This gluten prefents then to artifts a new kind of painting, 

 lefs folid, perhaps, than oil painting, which experience will 

 determine, but perhaps lefs fufceptible of changing by the 

 acYion of air and light. It would be attended with two great 

 advantages in printing figures or paintings — that of fpeedily 

 drying, and of not expofing the perfons who inhabit apart- 

 ments newly painted to any of thofe accidents frequently oc- 

 cafioned by oil painting. 



As the price of alcohol might render this painting dear, I 

 tried to prepare colours with glutinous varnifh made by means 

 of acetous acid ; but I was never able to mix it with any 

 oxide: the gluten immediately feparated itfelf, and was pre- 

 cipitated in a more folid form than it had before its folution: 

 it is therefore necefiary to employ alcohol; but the common 

 alcoholic products, fold commonly in the fhops under the 

 name of varni/bers' Jpirit of <wine, may be employed. 



If this painting were adopted, it would be necefiary that 

 the gluten fhould be found in fufficient quantity and at a low 

 price. It might be furnifhed by the {larch-makers, if they 

 iubftituted for their method of operation a procefs analogous 

 to that employed in the laboratories for feparating the {larch 

 from gluten. It would be eafy to conftru& a machine to tritu- 

 9 rate 



