The following receipt for marking fluid for blue-prints has given me satisfaction. The fluid Is composed of potassium oxalate, 1 ounce; gum arabic, 1 dram (60 grains); water, 6 ounces; cobalt-blue to color. William H. David.
Staten Island, N. Y.
A fluid which I find is as good as any 1 have ever used for writing white on blueprints Is made of equal parts of sal-soda and water. Another fluid, not as good, is made by mixing equal parts of borax and water. Both these fluids must be used with a fine-pointed pen; a pen with a blunt point will not work well.
Allegheny, Pa. C. W. Morrison.
I find the following means convenient for making a solution for marking white lines on blue-prints. I add to a small bottle of water enough washing soda to make a clear white line, then I add enough gum arabic to it to prevent spreading and making ragged lines. To make red lines I dip the pen in red ink and then add a little of the solution by means of the quill.
Cleveland, O. Ed. H. Remde.
A solution for marking on blue-prints, which I have tried with comparatively good success, is a very thick lime water. Have a good deal more lime than will dissolve, and shake up the bottle just before using, and it will not spread. Possibly this solution could be colored w}th red ink, but as I prefer the white I have never tried it. G. V.
For red writing on blue-prints, I take a piece of common washing soda the size of an ordinary bean and dissolve it in four tablespoonfuls of ordinary red writing ink to make a red fluid. The only way I know of to keep it from spreading too much is to use a fine pen to apply it with, and write fast so as not to allow to much of the fluid to get on the paper, for it will continue eating until it is dry. H. E. W.
In order to make red and white solutions for writing on blue-prints, dissolve a crystal of oxalate of potash about the size of a pea in an ink bottle full of water. This will give white lines on blue-prints; other potash solutions are yellowish. If this shows a tendency to run, owing to too great strength, add more water and thicken slightly with mucilage. Mix this with red or any other colored ink about half and half and writing may be done on the blueprints in colors corresponding to the inks used. W. H. Sargent.
St. Johnsbury, Vt.
Sometimes I find it necessary to make changes and corrections on blue-prints; to do this I use a solution of sodium carbonate and water, with a little red ink mixed in. This gives a very pleasing pink color to the changes which at the same time is very noticeable. The amount of sodium carbonate used depends upon the surface of the blue-print paper as some coarse-grained papers will look better if less soda is used and rice versa. However, the amount of powdered soda held on a five-cent piece dissolved in a bottle of water (Higgins ink bottle) gives very good results.
Sharon, Pa. R. F. Kiefer.
An excellent solution for retouching or marking in details on blue-prints can be prepared according to the following receipt. The solution consists of 75 grains of potassium oxalate dissolved in 1 ounce of water. If the solution is too thin and watery, it may be thickened by adding some kind of a gum preparation. It can be applied with a pen, as ordinary ink. The blue background is removed very rapidly by the solution, but it is important that the print be immediately washed, as the solution has a tendency to soak into the pores of the paper and blur the lines.
Olney, Ill. T. E. O'Donnell.