Stained Glass Glazing Compound

Here are some ideas, and several formulas/recipes you can use in glazing your larger panels.  The glazing will not only add strength to your larger windows, it will also seal the window against the outside elements.  (All the same, I personally would protect a stained glass window from the elements by placing it inside a new/existing exterior window.)

Recipe 1.

                   Dry ingredients:

4  parts - Whiting (Calcium Carbonate or chalk)

2  parts - Plaster of Paris

1 1/2  parts - Portland Cement

1/4  part - Lamp Black

                    Wet ingredients:

1 Part - Boiled Linseed Oil

1 1/2 to 2 parts  - Pure Gum Turpentine

Recipe 2

                    Dry Ingredients:

1 part - Calcium Carbonate (Whiting/Chalk)

1 part - Plaster of Paris

1/4 part - Lamp Black

                    Wet Ingredients:

1 part - Boiled Linseed Oil

1 part Mineral Spirits (Paint Thinner)

Mix your dry ingredients in a large container/bucket, then store for future use.  (I have found a bucket with a lid, plastic milk jugs, and canning jars to be satisfactory for storage; however the plastic in the jugs tend to deteriorate and become brittle after a few years which could cause a mess.)

When ready to glaze your project, mix up a small amount of the wet ingredients and add it little by little to the pre-mixed dry ingredients.  The resulting putty/glazing compound should be fairly stiff -- about peanut butter consistency.  

The working life of a batch of putty will be about one day.

I use a 2 to 3 inch length of wood, cut off a paint-stirring stick, to work the putty between the lead came and the glass.  Before ending for the day, I do a rough cleaning of the panel-it's easier to do it earlier rather than later.  Clean-up can be done with toilet paper or paper towels.  Final 'picking' can be done with  a small-diameter hardwood dowel either sharpened like a pencil, or flattened into a wedge.  Slightly undercut the putty for a crisp, clean lead line.

Acetone on a paper towel makes quick work on hard-to-remove putty on lead came or glass.  Consider using chemical-resistant gloves when working with acetone.