(d) Gilt frames may be cleaned by simply washing them with a small sponge, moistened with hot spirits of wine or oil of turpentine, the sponge only to be sufficiently wet to take off the dirt and fly-marks. They should not afterwards be wiped, but left to dry of themselves.
(e) Old ale is a good thing to wash any gilding with, as it acts at once upon the fly-dirt. Apply it with a soft rag; but for the ins and outs of carved work, a brush is necessary; wipe it nearly dry, and do not apply any water. Thus will you leave a thin coat of the glutinous isinglass of the finings on the face of the work, which will prevent the following flies’ fæces from fastening to the frame, as they otherwise would do.
(f) The Papier Zeitung recommends the following method of renovating gilt frames. It consists in applying with a camel-hair pencil a gum solution to which has been added gold bronze having the colour of the frame. Before mixing with the gum water the bronze must be washed with water until it runs off perfectly clear. If one application does not suffice, it may be repeated until the spot entirely disappears, but of course one coat must be dry before the next is applied. Spots treated in this way look very well at first, but it will not last, for it is not able to resist the moisture in the air unless it is specially prepared. For this purpose an ordinary bristle brush is rubbed with a piece of yellow wax until it is somewhat sticky, then it is passed very lightly over the spot several times as when dusting it. This gives it a very thin coat of wax that hardens in 2 or 3 days; in the meantime it must be protected against dust.
Sponge.—(a) First clean, wash, and squeeze out the sponges; then dip them into a 2 per cent. solution of potassium permanganate. Here they become quite brown (from separated manganic oxide); after 10 minutes, take out, wash in water, again well press, and dip into a 2 per cent. solution of oxalic acid [some prefer diluted sulphuric (1:20) or diluted hydrochloric acid (1:15)], in which they become perfectly white. Success mainly depends on the soaking in the permanganate solution; if they are macerated too short a time they do not become thoroughly white; if too long, they are apt to become rotten. (Siemens.)
(b) First clean the sponges by immersing in dilute hydrochloric acid. Then soak in a bleaching liquid, composed of 1 part sodium hyposulphite, 12 water, and 2 hydrochloric acid. After some time, remove and well wash. To the last wash-water a little glycerine is added in order to preserve the sponges soft. The liquid is best pressed out by passing the sponges through a clothes-wringer.
(c) Toilet sponges which have been in use, often become peculiarly slimy, fatty, and almost useless, owing to some action of the soap. Mere washing in distilled water does not remove the difficulty. It may be overcome by using fused calcium chloride. The sponge is pressed as much as possible, placed on a plate, the powdered calcium chloride is sprinkled upon it, and allowed to deliquesce upon the sponge. After about ½ hour, the sponge may be washed in water and dried, when it will become white. (Valta.)
(d) Soak the sponges, previously deprived of sand and dirt by beating and washing, in a 1 per cent. solution of potassium permanganate. Remove them, wash thoroughly with water, and press out the water. Next put them into a solution of ½ lb. sodium hyposulphite in 1 gal. water, to which 1 oz. oxalic acid has been added, and leave in the solution for 15 minutes. Finally, take out, and wash thoroughly. By this treatment the sponges are rendered perfectly white. Many sponges contain a more or less dark-coloured brownish core. If treated only with permanganate and acid, the core is either not bleached at all, or, if it has been somewhat bleached, the tint is apt to grow again darker. (Borham.)
(e) Soak for 10 minutes in a 2 per cent. solution of potash permanganate; then in a 2 per cent. solution of oxalic acid with the addition of a little sulphuric acid for about ½ hour; finally treat with a 2 per cent. solution of potash carbonate for ½ hour, wash, and dry. The solution of potash carbonate produces the yellow colour often particularly wanted. (Chem. and Drug.)
(f) A sponge employed in photographic manipulations for a few months loses all its valuable qualities, becoming black, hard, and greasy, and contaminating anything which it touches. To clean it, a solution of potash permanganate in water is prepared of such a strength that it appears of a wine colour, and into this the unserviceable sponge is immersed, and allowed to remain for some time. When taken out and squeezed, it is next put into a diluted muriatic acid of ordinary commercial quality, being immersed and kept saturated therein for some time as before. The most appropriate strength of this acid solution is about 10 parts water to 1 of acid. The sponge is taken out after sufficient treatment, squeezed well to free it from the acid, and then washed well in good spring water. When taken out, it will be found to be quite clean, to have again assumed its light colour, and to be free from all foreign matter. Sponges treated in this way become like new sponges, and can be used without any fear of their contaminating, even if employed for the filtration of neutral liquids. The main thing to be attended to in this plan of purifying sponge is to see that it is thoroughly saturated both by the permanganate and the acid solutions, which should be allowed ample time to soak through the mass; care must also be observed to wash the sponges thoroughly with plenty of water at the end of the operation. (Dr. J. Stinde.)
(g) When sponges get greasy, let them dry, and then work them with a small quantity of turpentine, and after a few minutes wash them with warm soap-and-water with a little bit of soda. This will get them quite clean with very little trouble. (E. T. Scott.)