Circular chip in Double Glazed window

car winscreens are often repaired with iirc epoxy.

They are, however, not deigned for penetrating holes. The resin is applied with some pressure and I suspect it would therefore leak through the hole. Glass repair tape would, at least, provide a seal.

How would you prevent moisture in the air between the panes from condensing in cold weather? Maybe you should just let it "breathe".

Or grind the hole a bit bigger to beable to introduce thru a small funnel as much ground oven-activated silica gel crystals before sealing the hole with whatever. I remember getting away with water-glass , thru MOTs , on a scratched windscreen

Chuck in some dessicant and use epoxy to plug the hole

"Water glass", aka sodium silicate, is what they used to use to preserve eggs (not sure if they were fresh or hard boiled). How would that fix a windscreen (which isn't double glazed in any case)?

I suspect to stand any chance the repair would need to be done on the hottest of summer days (not in mid winter) after a long dry spell.

One of my double glazing units took a direct hit from a stone off the lawn mower. It eventually corroded to blazes internally at the bottom as traces of water refluxed in the cavity.

It is very viscous and wets out cracks and is caustic enough that it doesn't smear on the windscreen wiper test. The price I expect you pay is that it makes the cracks propagate even faster through stress corrosion cracking. All alkalis will dissolve glass to some extent.

Glycerine might be a more innocuous choice of wetting agent to hide windscreen scratches.

If you want a good example of stress corrosion try wetting out with methanol on any random piece of plastic cutlery (remembering that it is toxic by inhalation and skin contact) and gentle flexing. You too can play at being Uri Geller...

Fresh eggs. My parents stored eggs that way.

That is very unusual, Normally glass would have so manystresses that it would star and the cracks grow over time . Brian

But they have access to the other side, and I think if it did penetrate, you would still need a windscreen. Brian

The car windscreen repair kit probably relies on the laminating plastic layer not being penetrated. The kit seals to the surface of the glass and a syringe is used to form a partial vacuum to then allow the epoxy filler to be drawn into the chip (without trapped air bubbles).

The problem with a hole in a DG unit is that moisture has already entered between the glass panels and unless this can be removed prior to sealing the hole condensation will always form inside the DG panel.

Mine also, in a bucket of waterglass in the pantry. We kept hens so always had a supply of eggs. That was in the early 1950's, so probably a hang-over from wartime, when everyone 'dug for victory' (and kept hens where they could). The preserved eggs were fine for cooking (in cakes etc), but apparently not so good for eating direct, as in boiled or fried.

we moved house in 1957 and I know my mother kept eggs that way in the new house.

It is quite possible to get double units made to order to the exact size that you need. If the window is glazed from the inside it may well be quite easy to replace the glass if it is not to large.

It didn't one one I had, but it did happen in summer and I put gaffer tape over the hole before it rained.

I've not used such kits, so.... If the resin is applied with pressure that suggests it's viscous, so no problem. If you do have the block the hole with clear epoxy first, what's the problem? As for humidity, I wouldn't lose sleep over it. You've got less vapour in wet winter air than in dry summer, and dg units don't normally stay sealed, and usually are fine.

Could that not be mitigated by warming the inner leaf, before sealing?

Warm air absorbs MORE moisture

Something that small I'd just use a small bead of clear silicon and get used to the flaw. The silicon will eventually discolour but no big deal.