What is Rebar and How is it Used?

Wire on left has been wrapped

What is rebar? I know they use it in building houses, but is there a different kind for glass? And where do you get it? I looked thru every question to you, but couldn't find anything that describes what and how you do it.
Thanks,
Linda

Answer

Hi Linda,

Rather than rambling on about rebar, I am giving you information written by Delphi Stained Glass and by Vic Rothman who owns a studio in NYC and does a lot of large windows as well as restoration work. I trust anything Vic has to say. I use him for a resource when I run into restoration problems.

VIC'S REBAR '101':

The term rebar means different things to different people. The round (sometime square) bars you see in church windows are actually called saddle bars. The bars are set into holes drilled into the window sash (removable window frame) or window frames (nonremovable).

The windows have ties soldered to them at the solder joints. In olden days they used lead as ties, today it's copper wires. These ties are twisted around the saddle bars. The purpose of the saddle bars is to prevent the windows from being blown into the building, not support. At one time stained glass was a real window out in the weather.

The ties should not be made very tight, but should be about one twist loose, thus the window can move in the wind. These bars are normally across the shortest distance.

Next is flat rebar solder directly to the stained glass. These bars are sometimes drilled into the sash and frames, or just run full length of the stained glass and put under moldings. These rebars act like the saddle bars, but because they
are soldered in place they also prevent the window from deflecting near the bars. They will not hold up the windows.

Rebar traditionally goes on the inside, because you do not want rain, snow etc getting on and corroding the bars if there were outside. If there is outside glazing you can put the rebar on the rear. The placement of rebar is not rocket science. It is very logical. You put them perpendicular to a lead line that might fold...parallel lines, glass borders, concentric
circles etc. In large windows you may need rebar running through the center to prevent the window from flexing. Rebar is VERY design and window location dependent. The size of the window does not matter. You can have a 12"x12" window that needs rebar and a 3'x3' that does not. If you design the lead lines well you need less rebar.

As for seeing the rebar get over it. Rebar is part of stained glass construction. If done right it should not detract from a good looking window.
Vic Rothman

Delphi says:
Reinforcement is necessary on larger windows. As a rule of thumb, a window more than three square feet should be reinforced. Either reinforcing bar or rod may be used for support. Be sure to consider this when designing the window so that the reinforcement does not intrude or compromise the design of the finished work.

In either case the reinforcement is soldered to the back of the panel in one of two ways. The bar should be pre-tinned before use. You will solder the bar in several places at intersecting lines on the window. Rough the areas to be soldered on the bar with steel wool. Apply flux and coat the areas with solder. Doing this will make soldering the bar to the window much easier. Place the bar on edge and solder to the window in the predetermined areas.

When using rod, a length of pre-tinned wire is first soldered at several intersecting lines on the window where the rod will sit. The rod rests on the wire which is twisted around it. Apply a bit of solder to the twisted wire. Solder either end of the rod (or bar) to the edge came. In most cases the rod or bar extends on either side of the panel and is “buried” in the wood casing of the window to provide optimum security. The casing is notched where the bar will fit and filled over to disguise it.

We use rods, and instead of twisting the wire we wrap both ends around the rod, cut off any excess, (circled with red in the picture above) then solder over the wire. We also paint the rods black before they put are wired place, then paint black over the soldered wire after the flux is wiped off.

Both bars and rods can be bought at any large hardware/home improvement store. Ask for mild steel for the rods, and zinc plated mild steel for the bars.

Here's what they look like:
Flat bars
Round Rods/bars