I am quite happy with the outcome to the new solar printer I brought home yesterday. On two counts. First off being the entire project, from laying out the functional components that needed to be built into the printer, even before the design layout, all the way through the building and testing, took all of two days. Working with my friend is like that. A good working discussion on what the printer is supposed to be able to do, then design it accordingly, take a break and begin finding parts.... All of which falls way outside normal corporate policy for R & D sessions.
The outside dimensions of the box are 26"x22"x12 1/2" (LxWxH) Total weight, including bulbs, comes in just under 36 pounds. The functional printing area is 20"x24", allowing for prints up to 20"x24", although that might be pushing things just a tad. What I can say at this time, pre-testing, that it is safe to say that printing at 16"x20" is guaranteed. There aren't a lot of photographers printing in hand coated mediums larger than 16"x20". One of the pluses to this design is that it can be scaled up, or down, without altering the basic design.
One of the design decisions to be made up front was the bulb size. Not just the length, but also the bulb type; T12 or T8. T12 bulbs are 1 1/2" diameter ~ T8 bulbs are 1" diameter. T8 bulbs are also the new bulbs replacing the older T12 bulb, which is becoming ever more difficult to locate, as they are being fazed out of production. The bulb is the focus of the printer, so choose wisely. I am not one to do a lot of internet research on what others are doing. I am more inclined to research the guts of a process or practice and go from there. Harry falls on the other side of things. He wants to know what everyone else has accomplished with any given practice. Here's what we found.
Most of the UV printers we came across that had photos of their lighting system, tended to show four bulbs or maybe six bulbs, separated by several inches in between. From my readings on this issue, that almost begs for banding on the print, unless the bulbs are a considerable distance from said print, and that would reduce the UV intensity quite a bit, considering the fall off rule of light to distance. One thing I have come to know well over the years of printing hand coated prints is that the intensity of the light source controls the tonal range of a print, lengthening or truncating the tonal range respectively, by decreasing or increasing said intensity, respectively. Which means that the output intensity of the UV light source, and distance to print, can make a very big difference. Being this is a prototype, it was designed to include two panels, one on either side of the printer, with two 3/8" slots (using bolts & wingnuts), allowing for altering the print height from the default 8", to 15", by raising the printer the full 7" allowed by the side panel slots. When the second printer is built I will know the optimal print height, and will build the printer to that printing height.
My solar printer has eight 24" T12 20W Blacklight tubes, spaced 3/4" between bulbs, sitting just a scad under 8" from the table top, with the final adjusted height to print approximately 1 1/2"- 2" when adding in the height of the printing frame. That puts the corrected print height to around 6", with 160W of UV light pouring over it. I chose the 3/4" separation between bulbs after reading about other UV printers, and banding. I came away with the notion that the separation distance between bulbs should be half the diameter of the bulb; thus a 1 1/2" bulb means 3/4" separation. That should negate any banding, even at close proximity to the print. Testing will either prove or disprove that theory.
A final note on the weight of the printing box. Harry doesn't skimp on building materials or in design. This printer is made from 3/4" high grade seven layer marine plywood for sides and mounting plate, with a 1/4" removable top plate. The mounting plate, with the four ballasts mounted on the top, and eight bulbs mounted on the opposite side (bottom) is of 3/4" material, and that mounting plate is secured from the bottom of the printer, which allows for turning the printer upside down and removing this mounting plate, with all the electronics on it, by removing four screws. Everything can be easily reached and any work done without much effort. There are no moving parts with the exception to the hinged printer door.
I don't believe I need mention that I am pretty proud of this printer, and even more excited about getting started with the dMax testing and negative testing to find the corrected printing time for silver, palladium, and gum prints. Now the printing can begin, and I will of course be writing extensively about it along the way, that you can be assured of....
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