Thanks JOhn and Spiros. I didn't realize that incandescent bulbs have stopped being produced which explains why I had so much trouble finding one. Fortunately, there is an alternative. The same type of UV lamp I have been using to cure UV cure resin, can be used for photo etching as long as it has wavelengths in the 350 to 400 nanometer range. These sorts of lamps are fairly cheap to get and I have one being delivered tomorrow.

I have the sandwich of photoresist , metal, and artwork in a dark box in my garage, so I will try to use it tomorrow after I get the new lamp. If that doesn't work, then I will repeat the process again. But I am hopeful it will work.

Great that you sorted out the lamp situation so effectively, my friend @clipper! Looking forward to the PE results tomorrow!

George (@gblair), Spiros (@fiveten), and John (@johnb), Still no luck with the PE process.

The light I bought is a UV cure light and according to MicroMark tech support, should work okay for this use. (I contacted them). However, increasing the exposure time and even exposing the film to sunlight afterwards still did not solve the problem of the developer washing away all the photoresist film from the brass. I've spent enough money on this that I do not want to spend any more getting a different lamp that still might not work. Tomorrow, I am going to try one last time and if that doesn't work, then I am going to shelve that part of this project and try a different approach which I am experimenting with this evening.

Namely, using my vinyl cutter to cut out plastic. I originally did not use this approach because I didn't think it could get down to that fine of detail. This is why I tried doing it by hand originally and ultimately thought that wasn't workable. This in turn led to me going down the PE rabbit hole. Anyway, tonight, I tried the vinyl cutter and it actually does cut fine enough. UNfortunately, even with the blade set at the maximum depth, it can't cut completely through the plastic I have (.005 inch) requiring me to finish the cuts by hand.

I cut a bunch of the louvers pieces so I could try this out. My first attempt at that I cut the part out, then tried to open up the vents and form the louvers, but the plastic disintegrated. For the second attempt, I cut and formed the louvers first, then removed the part from the plastic sheet. That was a little better, but not great. I tested it by gluing the part to my test mule. Even though I was careful to apply liquid cement sparingly, it oozed up out of the louvers and made a mess of them.

For the third attempt, I cut a small slot in the test mule and then glued another of the louver parts to it without opening up the louvers. When this dries, I will lightly sand it, and then I will try to form the louvers. I am also going to see if I can blend the edges of the part into the fuselage. This may require me cutting a shall ditch for the perimeter of the part.

Thanks for the links George (@gblair). I've looked at these as well as others previously and so far none really fits the bill. However, I may have hit upon a way to accomplish this.

I went back to try the plastic I did earlier this evening and that didn't work out either. I went online looking for options and one fellow mentions forming louvers with a leather punch in aluminum sheet. These would probably be too large for my purposes, but it got me to thinking that I might try using aluminum vent tape.

To experiment, I cut another slot in the test mule and then pressed some of this aluminum tape over the slot. Then I was going to mark the lines with a pencil and as I did so, I saw that what the pencil did was make indentations that looked surprisingly effective.

At first they were simply pressed into the aluminum tape and looked pretty good. I added a small bit of black wash and although I think these are a bit overdone now, the technique looks promising. It also occurred to me that I could put a small amount of clay in the slot to provided some semi soft backing for the aluminum tape. This might eliminate the recess that this first example has.

I'll experiment with this some more tomorrow. At the size of these louvers in 1/48 scale, I think this might be a possibility.

The aluminum tape looks good, Carl (@clipper). Using clay, or similar, might also help prevent distorting the louvers when handling the model.

The louvers look great, Carl (@clipper), and really do look like they are supposed to. My only worry would be that you are doing this on the actual model. So, "measure twice and tap once" would certainly apply. You would also think that the hardness of the plastic might play a role here. Looking forward to the results.

Very nice and promising technique, my friend @clipper! Looking forward to the results!

Thanks Spiros (@fiveten) and George (@gblair). This has been an interesting effort in learning. I think the PE problem is probably two things. The light I have is probably not strong enough and exposure time needs to increase. And I think the lines on my artwork are so thin, that they don't hold up to the developer when cleaning off the photoresist. I'll leave that experiment for a future day. I would like to master the PE process at some point.