[botticelli1972]

I use 4" wide jaw Vice Grips and 1/8 thick stainless steel plate as the backer. I have pieces of stainless for each size plate and one pair of Vice Grips. It is similar to clamps sold in the 19th century though the grips and the backing plate were one casting on the historic pieces. There is an example of this type of historic holder on the newdags site. The modern Vice Grips are sold for bending sheet metal and make a great handle to hold on to. They do do some damage to the plate surface, but I only use them at the extreme edge and that area is covered by either a mat or the rabbet of the frame if left un-matted.

If you look at the reverse of historic plates often you will see red sealing wax residue. This was used to mount the plates to a wooden dowel for polishing. Remember they didn’t use high speed buffers that would make heat to melt the wax, just slow steam and treadle power buffers and lots of hand polishing. Also, they bent the edges of the plates rearward and cut the corners off to keep the plates from catching the buffs and pulling them off the wax/dowel. This wax method is also why many historic plates are bent and wavy, they just yanked it off at the end.

[botticelli1972]

I also read that in Shalers’ book though I work in Becquerel and he in Mercury. I tried it and have found that the use of a UV filter adds about 2-3 stops to the exposure, though I did not noticed a change in image quality. I also tried a 80A blue filter thinking that it would send only a blue image to the plate. This resulted in the normal filter factor of 2 1/2 stops, but the image produced did appear to be "better" (though that is hard to quantify). I noticed this mostly on shooting a red brick building that otherwise didn’t record well.

My exposure guideline is adapted from one given by John Hurlock. For Becquerel I set the a digital light meter at ISO 100 and multiply the exposure by 70,000 (John recommends 80,000). I then add stops depending on the color of the scene, lots of vegetation requires two stops additional exposure, red brick building as mentioned above 3 stops extra, plus any filter factors if used. I also have to add a stop if I have been lazy at the polishing stage and have not gotten that "perfect polish." This gives a base Becquerel exposure of around 20 seconds at F/2.8 on a full sun day. I made a fairly good 4×5 sized exposure this weekend in Washington, DC full sun, lens stopped down to F/8 for depth of field, would have been 3 min. but I added two stops for the vegetation laden scene totaling 12 min for the exposure. I probably should have added another stop for good measure but I was in a hurry.

Larry Shutts

[Author]

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