replacing windows in a 1910 farmhouse. putting glass block in. how do you keep the mortar from oozing out when you place it in the sides? i got a 1" crack to fill on both sides.

Best way is to shim the window in with wedges and tuck point the gap. You’ll need a tuck pointer, they sell them at most hardware stores for less than $10

You can make it stickier by adding lime but what you really need to do is mix it as dry as you can and still be able to work it. Glass block don't absorb water and you know how squirrely they can be when you set them.

If you have the main field filled in you might try tacking something between the glass block and the window frame that will hold the mortar in place until it's stiff enough to finish but not so stiff you can't. I don't envy you.

Less sand, minimal water. Just enough to mix. Enough sand
so it comes off your utensil, but still sticks to the material. Been awhile
since i mixed mud. Horrible gig. What size bag/kind mortar are you using.

I’m not sure if you’re trying to lay each block individually or you bought a complete glass block window? If you’re trying to lay them individually it’s best to just build a frame (board on the bottom and the two sides) and lay them in the frame. They sell special glass block spacers and wire, once you get them all layed and they set up you can install the whole window, shim it in place and tuck point it in place. It’s so much easier that way! I forgot to mention they also sell glass block morter, just add water to the correct consistency.

Mix your own mud. Don't use the premixed stuff from the box stores, it has way too much sand in it. Use lime in the mix and mix it with minimal water.

Glass blocks suck to lay because, as said above, they don't absorb water.

Use an acrylic additive. It's meant to make cement stickier, especially for use on vertical surfaces.

acrylic additive

That stuff doesn't really increase the "stickiness" of mortar despite what the manufacturer claims. It is designed to create a chemical bond between two masonry surfaces as it cures. We use it a lot when parging over older masonry. It works well for that. It also increases the strength of mortar.

Be aware, when mixed directly into the mortar (as opposed to brushing it on the surface) it dramatically decreases open time.

Interesting. I used it once for some tuckpointing in my basement with old limestone block walls, and it seemed to work well. I just assumed it was "sticky", but that makes sense that it helps the chemical bond.

Hey Lugnut…..clean out your PM box !! Tried to send you a PM

Done Nessie, try again.

Swimming units not good.

When you spread your mud for the bed joint try to not have anymore excess mortar than you can. That will help you more than you realize , the more you tap around on glass block the more everything moves. Learned to lay them long before the spacers. Also don’t try to clean them up to soon, that’s another common mistake.

Another useful tip. If you're using wall ties to secure the glass block in the frame, use screws to secure the wall ties to the framing, not nails.

got it done yesterday.