Drilling holes in glass

I re-finished the bow window in the living room.

This involved sealing the shoddily-mounted outer glass in each of 15 separate window frames. I did this with good quality caulk. What I did not count on was condensation forming. I’ve done a reasonably good job of sealing them, as is evidenced by the fact that the lowest row- most exposed to sunlight for some reason- has spots of fog on them. The fogging is in between the two panes.

I’m unwilling to cut them away, they are clearly airtight from the outside right now. This is what I am considering, tell me if this makes even a smidgen of sense.

Assuming I can get the right bit, I am thinking of drilling a tiny hole- 1/64 inch perhaps- at the very top corner of each of the inside panes. This would release the vapor barrier and allow a tiny bit of air flow inside the panes. Not enough- I’d think- to eliminate the insulation properties, but enough to get rid of condensation. What is now fog will be fugly frost in the wintertime.

Is this a logical thing to do? And, do small glass drill bits even exist? I do have a highspeed Dremel, so going very slowly with little pressure as I drill is do-able.



It won’t work. That small iof a hole is far too small to let the moisture vent out, I think. What I would do is remove all the caulk again (I know, I know!), Heat each pane for a couple minutes with a hair dryer, to drive out the moisture, then reseal each one while it’s still warm.

Incidentally, if you ever do want to bore small holes in glass, I find the Dremel with a suitably-size silicon carbide (the blue ones) grinding bit works admirably. Don’t press hard, and back off the pressure frequently to allow the glass to cool–running it continuosly can overheat it, causing cracking.

Drill away but keep the drill tip wet with water or kerosene. Keeps the bits of glass from flying around.

Wear safety glasses or be prepared for a possible trip to the Opthamologist!
A bit of glass in the eye is difficult to find and to remove.

Incidently all commercial double glazed windows are hermetically sealed to keep out all moisture. Wood framse and caulk are NOT up to the job long term.

Well, shit. I’ve done the next logical thing. I’ve ground out a square hole at the corner of each of the 15 windows, exactly 7/8 " square. I’ve epoxied a 1" muffin fan into each hole.

By gum, that’ll dry those bastards out !!!


Okay. You are right of course, Q.E.D.. I put them up immediately after schmearing them with Windex. Hot breezy day, I wiped, I looked for streaking, I hefted and set them into the holes. Likely they were not as dry as dry could be…

…dammit. The scaffolding has been torn down, the lumber donated to my pal Donald/ scraps tossed to the county dump.

Okay. What if… I drill a hole, sift in silica gel, allow it to ABSORB all of the moisture, suck it out with my Shop-Vac brand vacuum with optional macro-tiny freakin’ hose nozzle, and caulk up each hole? Huh? Would that work? --desperate edge to voice–

I’d recommend against having that glass dust anywhere near your Dremel. I’ve heard of those things broken when the dust gets sucked into the motor and grinds them down.

Nah, the airflow runs from the intakes at the cord end to outlet near the chuck, so the outflowing air tends to blow any grinding dust away. Those Dremel engineers weer pretty smart. I’ve had mine for almost ten years now with no problems. The bearings are all sealed maintenance-free types.

A few comments:
First, the condensation may not be from inadequately dried glass. It could be acetic acid outgassing from your caulk as it cures.
Second, if your window frames are wood, they’ll probably absorb the moisture between the frames if you’re willing to give them a few weeks.
Third, be careful with that silica gel idea. If the gel contains too many fines, you’ll end up with what looks like dust adhering to the inner faces of your panes.

In a house I lived in a while ago, all the double glazed windows had a small hole drilled in the inner pane at the bottom corner and the outer pane in the top corner. I assume this is because they were not hermetically sealed (probably wood and caulk like yours)

Anyway, if you drill a small hole, then heat up the glass with a hair dryer or whatever, it should vapourize the liquid and force a fair amount of air out the hole, drawing it back in as it cools. Plug it with caulk when your done, and it is easy to repeat in two years when they’re bad again.

Jon Eakes showed this on his show. The result is “it might work”, but his directions seem to make sense. I guess you could seal them up when they finally clear.

Don’t forget the ‘bug filter’.

I haven’t been ignoring the good suggestions, I’ve been away. Still am. Won’t see that window till tomorrow evening, but Monday morning with the bright morning sun pouring in, I’ll take a look for condensation. Ditto at about 4pm, when those windows will be heated up by the slowly passing sunlight and be at their warmest- but no longer in direct sun. I figure if there’s condensation to gather, that’s when it will happen. When the glass is hot and air is hot inside, then glass loses sunlight and begins to cool, forming condensation.

I shall report back forthwith. :slight_smile:

( It’s scary to me that my seemingly stupid idea of drilling holes to vent it out has a web page detailing how to do it… )