Many thanks for all the much-appreciated help Col.

Ronald I reckon it's the best type of photography using sheet film sized anywhere between 5x4 " and 10x8 "

@Ronald The small portholes. An answer was provided but all thoughts greatly appreciated

@Chum444 The trick only works for small portholes where surface tension holds the resin in place. If the drop of resin is small there is very little bulging. You can correct this in the larger sizes by letting the resin half-set with the portholes facing down, then inverting them so that gravity pulls the outside face nearly flat. Any bulge on the internal side of the porthole can simply be filed down, of course, if you want to. I found that doing this trick with the hull of the Revell Flower class Corvette resulted in a sort of magnifying glass bulge which concentrated the internal lighting very well...

@jumpugly What about larger portholes or covers for gages? I’ve been using the clear dome from googly eyes.

@Chum444
Which idea are you asking about Chum?

@DodgyGeezer Good idea. How do you make the exterior surface flat?

Dodgy is on point again. If they are really small I use Micro Scale Krystal Klear.

@ColRay

No idea about large format photography but experimenting with the idea is something I’ve been doing for years. So long as it doesn’t harm me or others.

@ColRay For very small portholes, with the glazed area of about 0.1" diameter, a common trick is to put a drop of clear epoxy resin into the glazing cavity. It sets reasonably flat and seals well, of course.

Hey there Col !
I use Evergreen Scale Models 9006 J2 Clear Polystyrene Sheet .010" Thick (0.25mm)
A pack of two 6" x 12" sheets is usually under $5 USD.
I like the rigidity of it and it's easy to cut: just scribed and snap.
😉

Ronald Thanks for the info did.t think about using that type of plastic.

Because I still do large format photography I was wondering how a sheet of film that has been fixed will go > Col.

I have used various types of clear plastic to make my windows. The clear plastic containers found in your grocery store that contain any multitude of products from produce to bakery items.

The clear plastic of an envelope window is light weight.

The page protectors used in documents and binders works well too.