Biting on very soft steel plates may be accomplish ed by using the following mixture:—three ounces of warm water, four grains of tartaric acid, four drops of nitric or sulphuric acid, one drachm of corrosive sublimate.
1 also submit to the society a new method of gradu ating skies and other tints.
Incline the plate, by tilting it with two wedges, and pour the re-biting acid into a glass funnel, with a stick inserted in the tube, and kept steady by a twisted copper wire loop ; drop the acid on the dark part, and according to the colour of the tint the acid should be made to drop faster or slower, which is regulated by theraising and lowering the stick in the centre, and gives to the acid a tremulous motion, un til it is floated over the whole sky ; this obviates the old method of sweeping or feathering, which, from the quick action of the acid, occasions streaks to ap pear in the tints when the ground is taken off.
It is important that engravers should make use of the best acids, and perfectly free from adulteration. From the cheapness of sulphuric acid it is sometimes used with muriatic, to adulterate the nitric acid. The following tests will discover them:—dissolve a little nitrate of barytes in distilled water, and add it to a small quantity of the nitric acid in a phial or test tube; if a white precipitate is discovered at the bottom, sulphuric acid is present ; and muriatic acid will form, with a solution of nitrate of silver, a white cloudy precipitate ; should either of these effects take place, the acid is not fit for use.
The purest acids are those manufactured by Mr. Remnant, Smithfield-bars, who has made them some years for the use of engravers.
Since writing the foregoing account, I have dis covered means of making the ground adhere to the surface of the steel, without using acid to dull the surface.
Dissolve, by gentle heat (in a Florence flask), some powdered copal in oil of spike lavender, and evapo rate to a thick consistence; then to one ball of ground, add about one drachm ofthe copal solution, each having been made warm previous to mixing: lay the ground as before mentioned, avoiding too much heat; the ground may then be laid with the same facility as on runner. I am. sir. Ece. Ste.
s rEELE., Stu RionAno, a celebrated author, was horn at Dublin in 1671 or 1676. He received his education at the Charter House and at Oxford. His principal works are The Christian Hero, The Funeral, or Grief a la Mode, The Tender Husband, The Taller, The Guardian, The Conscious Lovers. He sat twice in Parliament, and was knighted by Geo. 1. in 1715. Broken in his fortune and his constitution, he quitted the world and died in Wales in 1727.