Fig. 15. Apparatus for impregnation by extraction of air fitted to manometer.
If the object is of some length but not too thick, the bell-glass may be fixed on a strong glass cylinder of a similar diameter having a ground edge (Fig. [15]), into which the object and the impregnating solution are then placed.
The following solutions, amongst others, may be recommended as suitable for impregnation:
(1) Shellac dissolved in alcohol.
(2) Solution of gum-dammar[94].
15 grammes of dammar are dissolved in 130 grammes of benzine, to which is added a solution of 20 grammes of clarified poppy seed oil in turpentine. If the solution becomes too thick it should be diluted with benzine and a small quantity of turpentine.
(3) Rice water or tapioca water[95].
(4) Dilute size.
(5) Waterglass solution.