This information was originally posted on Warner-Crivellero’s Glass Chat (www.warner-criv.com, Glass Chat). Some of it was compiled and edited then posted in the Featured Topics section for awhile, but was eventually removed.

Putty

There is more to putty then you think (or want to know). What I am about to write comes from 28 years experience and a large personal library.

Putty is made up of two basic ingredients: whiting and linseed oil. Then there are various things people add to the basic mix. I have broken this stuff into four categories.

1. Powders: whiting, plaster of Paris, dental plaster, field plaster, Portland cement
    
2. Liquids: raw linseed oil, boiled linseed oil
    
3. Thinners: mineral spirits, paint thinner, kerosene, white spirits, gasoline, turpentine
    
4. Driers: white lead, red lead, Japan drier

The powders add bulk (makes putty thick). Whiting should be used alone. Plaster absorbs moisture (moisture is the number 1 killer of building materials). Portland cement is so strong it attaches itself to the glass making restoration very hard. Plaster and Portland cement NOT good.

Liquids are for turning the whiting into the putty mix. Use 75% raw and 25% boiled linseed oil.

Thinners are for making the putty mix more liquid for brush putty work as opposed to pushing the putty with your fingers. These thinners evaporate quickly so that the putty sets up fast. This can be a problem as it shortens the life of the putty.

Driers are used to speed up the setting time of the putty. White and red lead are now illegal in the US. These things also shorten the life of the putty.

The last thing to add is color, if wanted.

The purpose of the putty is to add strength and to waterproof windows. For putty to work well, it needs to stay elastic for as long as possible. That's why thinners and driers are not so good.

So who cares? Well, as someone who living comes from stained glass restoration, I do because all stained glass windows will need restoration eventually. It's been obvious that the above problems can cause damage to a window in time. What is in time? 25+ years. Nothing happens in the first few years of a window’s life.

While most hobby work will end up in a land fill (please don't take offense) some of you might start making architectural and church windows. That is when this knowledge is important.

Inland cement, Miracle Mudd and other putties contain some of the NOT recommended ingredients. In the short term they all work, but if you want your work to last, they should be avoided. You decide what you need to do.

Rebar

Author: Vic

There is a lot of debate about rebarring. I will attempt to clarify what rebar is and how it is used.

The term rebar means different things to different people. The round or 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 (non-removable). The windows have ties soldered to them at the solder joints. In olden days lead ties were used, but 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 very tight, but should be about one twist loose so the window can move in the wind. These bars are normally across the shortest distance.

Next is flat rebar soldered directly to the stained glass panel. These bars are sometimes drilled into the sash and frames, or just run the full length of the panel 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.

Then there is true rebar. This can be thin brass strips referred to as "fins", which ranges from 1/4" to 1" wide and is about 1/32" thick. Fins are bent to conform to the lead or solder lines of the windows and are run in every direction.

Last year, I worked on a Tiffany window made about 1920 that was 4' x 9 1/2' (five people were needed to move it). The back was a maze of fins and the window was perfectly flat. In copper foil window, fins can also go between the glass during construction. As with any flat rebar, the strength comes from the width, not just the thickness, of the metal. Thus a 1" wide bar is stronger than a 1/4" bar.

Rebar traditionally goes on the inside because you do not want rain, snow, etc. getting on it and corroding the bars as would happen if they 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. Rebar is placed perpendicular to any 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" x 12" window that needs rebar and a 3' x 3' one 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.

Plating (using multiple layers of glass)

Primary author: Vic

Additional information: Ernie

Gay posted the following message: “I have never done a layered panel—so far, but am interested in trying one. Can anyone give me some input about the techniques involved?”, to which Vic responded.

Vic:

First build the window (base layer). Plates can go on the front or back (i.e., Tiffany, LaFarge). They can be the same size and shape as the piece below, or can cover many pieces, or a part of a piece.

Foil:

Do not bead where the plates are going to go, just tin. The easiest way to attach the plate is to wrap the plate in foil and tin it. Place it on top of base window and solder WITHOUT using any flux. Be careful not to let the solder get between the plates. If the plate is the same size as the piece it fits against, you can also use wide foil and foil both pieces of glass together and solder to the base window.

Lead:

Do not putty where the plates are going because dust will collect between the plates when the putty dries. You can wrap the plates in lead and solder to the base; tin the lead first, then solder WITHOUT using flux. You can also use "high" heart lead and put two pieces of glass together. You can even lead a second window on top of the base if you want to. To do this, use a smaller "H" lead then the lead below and tack solder the interior leads to the base, and fully solder the perimeter lead to the base. Lightly putty the plate lead with a dry putty; do not push it under the lead too hard.

Oddy says to vent the plates to prevent moisture from collecting between them. I have restored many Tiffany, LaFarge, and other 100-year-old plated windows and never seen moisture between the plates. I have a foiled window with plates that I made 20 years ago that has lived its entire life in a bathroom without collecting moisture between the plates. Seal the plates all around. If you leave spaces, dirt and moisture WILL get in. As Oddy also said, if you use many plates you will add weight to the window that may cause problems if the window is not properly rebarred.

Ernie:

There really isn't just one way to plate or layer glass to achieve the various results that can be gotten. There are times when you might add a layer of clear textured such as baroque glass over the whole face of your scene to create the impression of swirling water. There will be times when it's used to add shading to an object or flower petal where you attach it to the back just behind a few pieces, one piece at a time. At other times it'll be an area that is covered by a single piece of glass. Robert Oddy used the solder lines on a plated piece of glass to give motion to an owls wings. Plating is done both from the back as well as the front depending on what look you are trying to achieve. Traditionally it was only done on the back but today the old rules no longer apply. These are just a couple of ways to use plating and frankly it would take a book to cover them all. I'm not sure that I could even list them if I tried since someone is always coming up with new ways to use old techniques in exciting new ways.