Installing Stained Glass Panels

Can I install my panel behind the existing glazing with silicon caulk?

Leave the silicon, or any other caulk for the bathtub. If you ever need to remove the panel for repair, it will be extremely difficult. You will have broken glass and ruined lead when you try to pry that panel out of that stuff.

If you think you will not ever remove the panel, think again. Silicon caulk plus humidity will be the reason you have to remove it. There is a very good probability that you will have condensation (fogging) between the clear glass glazing and your stained glass panel when it is sealed with caulk. Over time the condensation will result in a permanent haze on the glass. It will turn ugly, and the rework will be even uglier to deal with. Commercial double glazed windows include a desiccant to absorb trapped humidity, or they purge the space with dry nitrogen before sealing. 

The easiest solution is to let it breath. Install the panel without sealing it. Use wood molding to cover the edge. Just paint it to match the other trim. You want at least 1/8" between your panel and the existing glass. Usually, you can put a strip of putty tape or foam tape on the existing frame to get this spacing. Leave some gaps in the tape along the bottom and top of the panel. These are your air holes. When the sun heats the glass and the air space in between, you will get a natural convection air flow from bottom to top between your molding and the door frame, and through the gaps in the tape. 

This is a small airflow, but it is sufficient to keep things clear. If you have large gaps, you could have a problem with dust infiltration. So don't go overboard. Don't forget to properly support the weight of your panel at the bottom. H came will crush, the bottom portion of your panel will sag, and glass will fall out if you don't. If you plan it right, you will have a support strip in the H channel under each lead intersection with the border, with your air gaps in support and spacing tape between 
these points. You can fix the panel in place in the frame with tacks driven into the frame, slightly crushing the outside of the H border came, every 8 to 12 inches or so. The trim molding will hide this ugly fact of life. 

How tight should my panel fit the frame?

There should be at least 1/16-inch up to 1/8-inch from the outside edge of your border came to the edge of the rabbet in the frame on all sides of your panel to allow for expansion and contraction of materials. The bottom edge of the panel is usually supported by a 1/16-inch shim under every piece of glass in the panel, or under each joint in the edge of the panel. Popsicle sticks or tongue depressors work great for this. Don't forget to fill the channel in the came with a small piece of wood or glass over the shim so the heart of the came, and not the thin edge of the face supports the weight of the panel. 

In assembling your panel, be very mindful of growth. This can defeat all your best design efforts. A panel should not fit tight within a frame. If there is a tight fit it will buckle and fail over time. The panel will expand and contract with solar heating. A wood frame will expand with humidity. An aluminum frame will expand with solar heating. If your panel is a tight fit in the frame, when everything shrinks, you are 
OK. But, when everything expands, something is going to give. And that something is almost always your glorious work of art, and not the simple frame that holds it. 

Some artists use 1/2-inch “H” came for the outside border. This wider came will allow you to cut off some of the lead with tin snips to custom fit a panel within a frame. Some have found this particularly helpful when that old wooden rectangular frame turns out to be a rhomboid or trapezoid. 

How do I remove the wood panel in cabinet doors so I can install my stained glass panels?

You may want to find a woodworker friend to help you with this one. Most of today's high-end frame & panel cabinet door construction does not lend itself to easily removing the wood panel and inserting a stained glass panel. 

Rails and stiles for the frame are cut on molding machines, then glued together around the panel. The panel "floats" in a U-shaped channel in the frame. This allows the panel to expand and contract with changes in humidity while preventing it from splitting or prying the frame apart. The glue joints between rails and stiles are stronger than the wood itself. You will not be able to disassemble the frame without destroying it. The same may go for removing the panel. 

The U-channel in the frame is probably 1/4-inch wide and deep. The back of the frame probably has 1/8-inch of material forming the backside of the U-channel. As a woodworker, I would probably set up a jig and use a router to remove the backside of the U-channel. I would use a spiral up-cutter in the router set to 1/8-inch depth. With the backside of the U-channel cut away, the panel should just 
lift out of the frame. This would leave a 1/4-inch wide by 3/8-inch deep rabbet for installing the stained glass panel. The rounded corners from the cutter can be squared with a hand chisel. 

Your woodworker friend might be able to use the removed panels in other projects. I would offer them as compensation for the assistance. Throw in a sun catcher when the job is done, and you can probably get help whenever you need it. 

The front side of the frame probably has a molded profile, which will prevent you from cutting the rabbet any deeper. When you install the stained glass panel in the rabbet you have, you will not have enough depth to install any type of molding to hold the panel, or cover the edges of the rabbet. You could hold the panel in place with tacks and finish the edge with glazing putty. You could put a finish on the rabbet, and install the panel with clips. (You can buy these clips from woodworking stores or on-line catalogs.) Or you could get your woodworking friend to cut some battens that would screw to the backside of the frame and cover the rabbet & panel edge. This would create a raised "frame" on the back of the doorframe, which you may or may not like. And, you would have to put a matching finish on the battens. Or, you could go to a cabinet shop and have them make new frames to your specifications and use the old doors for firewood. 

How do I do small panels for existing windows? Can I use copper foil construction?

Foil construction (done correctly) will provide an environmental seal and will have more than enough structural strength in a 9x12 panel. Pay attention to cleaning to remove the flux residue after soldering so you won't have acid corrosion, particularly if you install the stained glass panel behind the existing glazing. The clear glazing in front of the stained glass panel has advantages and disadvantages. It does provide protection and makes window cleaning easier, but some people object to the sunlight glare obscuring the outside view of the window. The inside view is relatively unaffected. You will have to pay attention to the possibility of condensation between the panels in installation and leave breather holes inside, or seal the panels together with a desiccant in the border seal. 

Measure the rabbet width in your frame & mullions. It will be something like 1/4 or 3/8 inches wide (& deep). Measure the rabbet-to-rabbet opening, and don't assume the frame is square. Take several measurements to see what you have to deal with. This is the opening the glass will mount into, not the viewing area. Lets assume the opening is a perfect 9x12 with 1/4-inch rabbet widths. Subtract 1/16 inch from each side to allow for expansion and contraction of the wood frame with moisture and glass panel with solar heating. You don't want the frame compressing your panel and causing it to buckle. This is a common failure caused by poor installation. Your 
glass area is now 8 7/8 by 11 7/8 for foil construction. (Lead came construction will have different dimensions for border lead and glass area.) 

The edge of your panel will sit in the rabbet and will not be visible in the viewing area of the window. Aesthetics rules say your glass should not disappear in the rabbet. There should be a visible lead border on the edge of the panel in the viewing area of the frame. If you used a foil width of 3/4 inch for the panel border, this would give you a visible border of 1/8 inch within the frame. 

To install the panel, put a bead of putty (glazing compound) in the corner of the rabbet. Press your panel, centered in the frame to leave that 1/16-inch all around, into the putty until it squeezes into the viewing area. Secure the panel to the frame with glazier’s points or tacks, just as you would secure a clear glass windowpane. Glaze the rabbet just like you would for ordinary glass installation. Trim the putty squeeze-out in the viewing area on the other side to leave a clean edge. You're done. It should last a long, long time. 

How should I install a bathroom window?

Gaps on the sides generally do not help airflow, not much anyway, and are not of concern. Convection airflow is from bottom to top. As the air is heated between the panels, the warm air rises, flows out the top, and cooler air enters at the bottom. If you suspended a hair between the panels, you would not see it move. We are not talking about cubic feet per minute airflows. It is minute. And yes, unsealed molding nailed to the frame is enough of an air gap in low humidity conditions. But you want to make sure you don't seal it with paint when you paint the molding.

In a bathroom most of your humidity and condensation will be inside, when it is cool outside and you take a "steam bath". But nothing is hermetically sealed and some of that moisture will find its way between the panels. It is possible, in a poorly vented bathroom that you could get some condensation on the inside of your stained glass panel, since it will be exposed to the outside cooler air.

If you have air conditioning inside the house and keep the house on the cool side you may get some condensation between the panels.

In either of these extreme cases, I would probably put in some 1/16" spacers under the top and bottom molding to ensure a good airflow.

If you are uncertain about where you fall in the humidity spectrum, and you want to keep those tiny spiders or other critters from getting in, you may want to put in 1/32" spacers. A thin washer every foot or so would do. If the molding gets nailed down flush between spacers, don't worry, you would still have enough air gap to control condensation.

Don't overly fret and worry this issue. It is important, but not overly serious. A little understanding of the environment, a little thought and preplanning, and you will be successful.

Outside protective glazing is really a matter of preference. If you install it with the same airflow considerations, you will control the condensation problem. Most of this type of installation is to protect the stained glass window from damage (inner city rock throwing) and dirt accumulation (a single sheet of glass is much easier to clean than a stained glass panel). The major disadvantage is that glare off the glazing obscures the view of the window from the outside. Many of the earlier installations to protect church windows from damage used Lexan. Now 30 years later they are regretting it. The stuff degraded in ultraviolet light to a dingy brown color, completely obscuring the windows. Most of the stuff you will read on the protective glazing subject will be subjective opinions. What I have read and sorted out has led me to what I stated above, it is a matter of personal preference. But if you do it, use glass, not plastic. If you need protection, use thick tempered glass. That's my 2 cents worth.