I am a firm believer that necessity is the mother of invention. Let’s face it, most people do not design and build just for the enjoyment of designing and building. . . at least I don’t. Many years ago I decided to purchase the Zone VI Compensating Developing Timer and I have used it ever since. This is a great darkroom tool, and I would not process film nor paper without it.
The biggest problem I had when I first got my timer was trying to come up with a way to mount the sensor to my trays. Since by this time in my photographic career I was tray processing sheet film, I had no use for tanks and what was sorely missing was some sort of bracket to hold the sensor in the tray. I tried tape and even a plastic close pin. Nothing seemed to work, so it was off to think a bit. I do my best thinking while taking a nap.
After some time contemplating the situation, I finally visualized a clamping device that could be attached to the lip of a tray. I decided that it needed to be made of a tough material that wasn’t affected by chemistry and would be easy to keep clean. So I chose to make my clamp from a chunk of Acrylic.
I dug out an old hunk of scrap Acrylic from the junk box and began working it into shape with a band saw and vertical mill. What I eventually came up with was a prototype temperature clamp that I have been using for over ten years now. Take a look at the accompanying photos and you will see a very well used piece of darkroom equipment.
I have always wanted to improve a little more on my original design, but just never got around to it, until now. Though my prototype shows no signs of degradation, it is well stained from the Amidol days and my biggest concern is that there might come a time when the Acrylic would fail. You know how nothing ever fails except when you really need it. I could envision this thing breaking in the middle of a printing session or even worse, in total darkness during a film run. Though from careful examination of the original, I can see no signs of failure. Still, I always like having a spare on hand.
So, having decided I need a spare clamp it was time to do a little redesign and then off to the shop to cut up some Acrylic. I beefed up the clamp a little and reworked it so it could be drilled for both sizes of probes that came with the original timer. Yes, we do have a spare timer also. The only thing is the spare is the newer unit and uses the larger probe. My original Zone VI Compensating Developing Timer came with a probe with an OD of 0.1875 inches, while the newer model has a probe diameter of 0.250 inches.
As with most projects of this type, it is just as easy to make several as it is to make one. I cut up all of the Acrylic that I had on hand and made a handful of Probe Brackets. I still have some hardware on order, but I already feel better knowing I have spare parts on hand.