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Description of the Process of Daguerreotype, and Bemarks on 

 the Action of Light in that process, both in respect to Land- 

 scape and Miniature Portraits.* By Mr Thomas David- 

 son, Optician. Communicated by the Society of Arts for 

 Scotland. 



12 Royal Exchange, Edinburgh, 

 9th November 1840. 



Sir, — In submitting to the consideration of your Society 

 the few following remarks concerning my method of taking Da- 

 guerreotype pictures, &c, I beg leave most respectfully to state 

 that, in the first part of the process, I differ from Daguerre, as 

 I use no oil Avhatever in the preparation. I merely take a 

 new plate, and polish it with the diluted acid, and a little fine 

 rottenstone, changing the cotton and rottenstone two or three 

 times, and then take a clean bundle of cotton-wool, which I 

 dip or daub on a little fine dry Tripoli, and with that give a 

 finishing lustre to the plate. I then lay the plate into a frame 

 which exactly fits the iodine-box with its outer edge, while 



the plate fits the 

 rest on like this, 

 the iodine from 



plate 



aperture exactly, having a ledge to 



The use of this frame is to prevent 

 attacking the edge of the plate and 

 spoiling it, before the centre has got enough of iodine. The 

 iodine-box which I use is about 3 inches from the bottom to 

 the face of the plate, which, in summer, takes from 1£ to 2 

 minutes in being iodinized. The plate should be reversed in 

 its position while the operation is going on, so that it may be 

 more regularly coated ; and the lid of the box should be opened 

 and shut very gently, lest it raise up some particles of iodine, 

 which would attack the plate and cover it with black spots. 

 The plate is next to be put into the frame, and exposed to 

 the action of light in the camera, where, in summer, it should 

 remain from 6 to 10 minutes, according to the intensity of 

 the light and the time of the day. At present, an exposure 

 for 15 minutes in the camera will be required. 



The next part of the process is the mercurializing of the 

 picture, which is certainly the most difficult part of the whole ; 



* Read before the Society of Arts for Scotland November 23. 1840. 



