Builder's & Number plates

Of course, a printing shop could make nice zinc plates with their "autotype" process, but, being the eternal tinkerer, I wanted to do it all by myself, and in brass, too...

There's a Dynamark (formerly 3M) material called "i.n.t." (image'n'transfer) that enables you to make your own "dry-transfer letters" - perhaps you remember "Letraset" and similar products, used for graphic arts titling and headlines before computers and laser printers? i.n.t. is an imageable material, used by, among others, ad agencies and graphic artists - and some crazy animators...

First, a lithographic negative is made of the artwork (for all the graphics I need to do in my animation work, I have a lithographic repro camera in my darkroom/workshop, lucky me!), and then the i.n.t. is exposed with an UV-fluorescent lamp through the negative.

Here I develop a transfer image of the builders plate - messy work.

After developing, I got a sheet with the image in a sticky, tarry-like black substance, which transfers by pressure (ball point pen, for instance), here to a piece of sandpapered brass. The surface has to be clean!

Then, etching. Here the brass plate (cut to size) is immersed in a strong solution of ferric chloride (FeCl3), which slowly etches away the surface unprotected by the transfer. Acid etching would be too vigorous for the i.n.t. - gas bubbles would lift the transfer off the metal.

An hour of immersion in the FeCl3 bath only etches away less than 1/10th of a mm (a few thou), but that's enough to get the necessary relief for the next step...

... after removing the transfer, rinsing & drying, of course: I spray painted the plate matte black, and used 600 grit emery paper on a flat surface to polish the raised letters "out" from the paint.


Even with all the literature I have obtained, it was very hard to determine exactly how the plates looked on the 3003 - the maker's plate design changed in 1873 to Burnham, Parry, Williams & Co., but in 1872 it should still have been as shown here, i.e. M. Baird. But the book "The American Locomotive" by John H. White shows a drawing of the 1870 Baldwin loco No. 2550, with a plate that has only "PHILA." on the bottom. Does anybody of you have any literature that could elucidate on this? I've drawn these as close to prototype as I could - but if I can get some definitive info, I'll etch new plates...



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