Work on the display case has followed three areas.
Room Finishing
This part is time consuming and mundane. The room that the case is in is a combination office, workout room and more than a little bit of storage space. That means when the walls get painted there’s a lot of stuff to move out of the way. Most of it is “keeper” stuff, but some of it, particularly old framed prints will probably be donated.
The paint on this room went back to its original finishing back in 2003. It was really in pretty good shape except for the part where someone cut a big hole in the wall. It did have years of marking the heights of children, nieces, and now grandchildren.
The entire room got a new coat of paint that more or less matches the room next door. Then trim wood was painted to match the finish of the bookcase. Because metal studs were used the trim was fastened with “trim” screws. Nails won’t hold particularly well in metal studs and moving the case in and out of its niche would be likely to pull on the trim a bit.
Cabinet Design and Ventilation design
The cabinet itself has had some treatment.
The back of the case, which was just thin Masonite covered with a finish plastic was fairly reactive to UV light. To knock that down the display parts of the case were sprayed with “Chalkboard” paint. In fluorescent mineral discussions this was said to be one of the paints that had the least reactivity with display lights.
The top section of the case will hold the shortwave lights, power connections, and a fair amount of wiring. The shortwave fluorescent tubes require ventilation to keep them cool. I’ve put two 92mm computer fans on the back of the bookcase blowing out and have put two more fan covers with sponge material in it to act as an air inlet and a bit of a dust filter.
The display section of the bookcase will have three shelves. We’ve tentatively decided to have full spectrum in the top section. That is White light, Longwave, Midwave, and Shortwave UV. The middle shelf gets only longwave UV since it is simpler and more rocks that we have are active with longwave.
The bottom of the three display shelve will be white light only.
Under that shelf will be pull-out shelves that are storage/display and a drawer for bigger stuff. For all the samples it’s important to keep the type description and location found with the rock. The drawer can’t be a jumble so I’ve worked out a divider system. I also found some “carpet” at Menards that is made for things like boat floors or car trunks. It’s nice and black and not UV reactive (although this shouldn’t come into play since the drawers aren’t under UV). It’s also relatively cheap.
I’ve taken an inch and a quarter off the back of the three internal shelves (the two UV display shelves and the shortwave/equipment shelf) and drilled new holes in the side of the bookcase to support that so that an OP2 sliding panel can be place in front of the shelf. OP2 is a cast acrylic material used by museums to shield artifacts from UV light and to shield people from UV displays. It’s sibling OP3 is used primarily in picture frames and is extruded. Directly in front of a document the difference isn’t noticeable, but looking through the case will be free of flaws while the extruded will have ripples that will distort objects at more than contact distance.
Lighting Design
I’ve read a couple of laments that there are no commercially available, hobby grade UV display systems. Now I believe it. The lighting design has turned into much more of a R&D project than I originally envisioned.
UV LEDs come in display light form if you want 400nm. These are unfiltered and are mainly used for black-light parties, fluorescent art, and clubs. There are smaller versions used for counterfeit bill detection. They also have a very significant amount of visible light.
Reasonably high-powered UV light down around 365nm is much harder to come by. Basically the only commercial source here is flashlights and only some of those are filtered. We have two 365nm flashlights, one filtered and the other (which was cheap) is almost as bright with visible light as a regular flashlight. (It’s actually nowhere near as bright, but if you want to see rocks glowing against a dark background you need the filtered light). Even shortwave LEDs generate some visible light which is the reason for the filter.
So a lot of the last few weeks has been perusing eBay and Amazon and AliExpress for LED that can be turned into display lights. And it isn’t just the LEDs. There has to be a way to correctly power the LEDs – most of them need a specific current rather than a specific voltage. That current produces heat so there needs to be a heat-sink behind the chips to keep them from overheating. Then there has to be a way to mount the light assembly to the bottom of a shelf.
Ordering this stuff from any vendor really means ordering from China. Digi-Key probably has some stuff in local stock, but it’s really expensive (although it does have matching engineering specifications). A lot of this too has a try, see how it works, and go from there factor so it isn’t like I’ve ordered a big batch of stuff and it’s going to come in all at once. It also means a two or three week wait between ordering and seeing if what you tried works. I spent a week looking for how to mount the filter in front of the LED and I came to the conclusion that I’m probably just going to have to 3D print it myself.
Back to shelf design, I also want the shelves to be removable so I need to work out a way to make the wires for the lights disconnectable.
The power switching for all those different lights… That’s probably a different entry.
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