Epoxy or what?

[ivconic]

What on earth is 'purpen'?? We can't advise you on it's use if we haven't any idea what it is....
I've never seen a supplier of soluble-coating enamelled wire, these days it's normally heat-activated, by passing a high current through the winding. There's a good U.K distributor whose site is worth a look at:
https://wires.co.uk/

"Purpen" is polyurethane foam.
And abbreviation "purpen" is unhappily adopted by me and other people from this region, from the past where we had it in local shops imported mostly from Germany, that's actually a German abbreviation from German manufacturer which produced it at the time (30-40 years ago).
So it's actually polyurethane foam.
Sorry for confusion!

[ivconic]

Probably it is not air per se, that help drying Purpen, but relative humidity of air.
So a little moisture inside can help and ad no harm to coil circuit.
And Purpen should be fresh one.

I highly suspect that it is different kind of "chemistry" than ordinary polyurethane foam is.
Because i saw no moisture nor water inside old Cscope coils when i opened them.
Inside is dry as desert! Very tough to open it too!
And "foam" is very well distributed inside, fitting whole inner space perfectly.
Only way to remove it is to use sharp knife and cut chunk by chunk of it.
I did that several times with very old Cscope coils which are uselles for to be matched with todays detectors, yet plastic enclosure is ultra high quality made and i just wanted to preserve those for future use.
Besides; there were few semiconductors included inside, so plain windings couldn't be used properly even if inductances were close to what i needed at the time.
That's how i had the opportunity to see what's inside...

[WM6]

Because i saw no moisture nor water inside old Cscope coils when i opened them.

Sure not, after hardening it is water resistant, even with isolative properties.

But for hardening it need enough humidity in air, otherwise it not react properly and remain in soft stage:

[Skippy]

Regarding the problem of getting moisture into materials that need it for curing, I came across this interweb article. It shows how to make silicone 'bath sealant' useable even for large quantities, using cornflour. I have not tried the method out.
http://www.instructables.com/id/How-...ru-Substitute/

[jladre]

About coil shell i just done hammering 3 coil shell.. I found out that a shell must have enough air space inside in order to maintain the coil quality before putting it in shell. Putting epoxy, fiberglass, polyurethane, us not a good idea.

[kuzen]

Do you mix foam,,,A compenant POLİURATAN B compenant İZOSİYANAT.this mix hard but,you have mix machine