Silicon Archival???


SPFG, Supreme Picture Framing God
Jun 11, 2004
Edwardsburg, MI
I am framing several very valuable prints and my customer would like to float them between glass. I am planning on using a narrow moulding with enough space to use museum glass then a spacer, the print mulberry hinged to a museum board cut slightly smaller than the print and then the museum board adhered to a piece of clear picture glass with silicon adhesive. The entire package would then be set into the frame and held in place with quarter rounds.

Is silicon the best adhesive to use from an archival standpoint. Someone else suggested acid free ATG tape, but I'm afraid it would give out after a while.

Do you see any other problems with my construction?

The pieces range in size from 18" X 18" to almost 40" X 60".

I appreciate any insight anyone might enlighten me with. (How's that for good English?)

Dave Makielski

"If you're going through ****...just keep going!"
"Someone else suggested acid free ATG tape, but I'm afraid it would give out after a while."

I tried one like that and the ATG lasted through the winter. When it got hot in July, it let go. I also know that there has to be a lot of out gassing from silicon because it sure does stink. Maybe in small amounts it would be OK. Hopefully Hugh or Jim Miller will give us the real answer.
As a fellow framer from Michigan I would seriously try to discourage this type of framing in our climate especially since you are framing "very valuable prints". We go from 10% in the winter to up to 100% in the summer. There is also the factor of cold exterior walls and fireplace flues.

Take a look at any window during the winter and you will see serious condensation / ice.
Man, I can't wait to hear the proper advice on THIS one...

The use of silicon is sorta the dirty little secret that lots of us do .... kinda like a closet desire (just a desire..???) to log onto porn sites ...


Would your concern be the adhesive properties of the silicon because of changing heat and humidity or would it be fear of condensation?

The work would hang in a heated/humidified and air-conditioned climate...however, of course, not up to museum standards.

I have had many clients over the years that say that the envirnment is climate controlled. In many instances they are not (24-7-365).

If the client insists on this frame package make sure they are aware of the hazards of what they are requesting, where it is to be hung and how it is to be maintained by them.

There have been several posts in the past about the various types of silicon and the various chemisties of them. I can't remember the exact version, but it does not off gas citric acid. I have never used this version of silicon.

This is not a traditionally recommended method of framing valuable prints, but I do like the fact that you're using spacers, and have a 4-ply backboard in there. That will add some buffering capacity to help the paper support absorb and desorb water with changes in temperature.

Make sure the client knows that there is risk of condensation and breakage, and choosing the display area carefully (away from potential temperature extremes such as windows, heating vents etc.)

Silicone can have problems, and I'm copying an earlier reply from an objects conservator who has some experence with silicone adhesives. Perhaps a good quality tape like 3M #415, or the 3M tape Jim Miller suggests for encapsuation would be a better substitution.

"The off-gassing thing with fresh silicone caulk is pretty well known. Silcone rubber will turn a lead coupon white in short order as the acetic acid forms lead acetate crystals on the surface. In my opinion, the biggest problem with using silicone caulk as an adhesive how difficult it is to get off the object. Even if the object is reasonably hard it can still stain. I have seen silicone staining on stone arrowheads and tools that were mounting with it. Even glazed ceramics can have small micro-fissures in the glazing that allow the oil from the silicone to penetrate. It is nearly impossible to get out. The only thing you will ever be 100% certain you can get it off of is glass. On metals , the residual acid will etch the surface guaranteed.

There is also another aspect of using silicone caulk that you might want to alert the framers to. This not yet proven but there is some evidence that silicone caulk will give off some sort of volatile oily component over time. It has been noted on the inside of exhibit cases where the glass was siliconed in. The glass gets this hazy look to it. It is very difficult to clean off. I have heard from exhibit guys that all they can do is smear it over to the side as best they can so that the central view field is not affected. I don't know if it is a certain kind of silicone caulk or if they all do it.

If you want to post any of this message to your list that is fine with me.

good luck


Scott Carrlee, Conservator
Alaska State Museum"

Dave, the only "safe" silicon caulk that I ever ran across was one that is "food grade", also it is strangely enough "electronics grade" specifically for sealing gold contacts. (don't know if it would work on my crown that is leaking)

It's designation is GE 860 or 680 or something like that. All I know is that; of all the caulks in the GE line-up, this is the one that NOBODY stocks or has ever seen..... I can't even remember where we used to get it. Graingers?? maybe.

What do you have against just plain old white glue. It's ph neutral. It doesn't off gass, and it's reversable. Scrap it off with a razorblade.
It's not something most people think of, but it does stick to glass. It is one of the only glues used to repair bone china. Thin layer on both side, let air for about a minute then stick together.


I'm not trying to be a kill joy here, but the reason white glue works for some types of pottery is that the interior (broken edges) is porous. White glue would not bond glazed surfaces together well, nor is it a good choice for smooth surfaced glass.

You could use Yes paste. It would be better than white glue because it is so low in moisture.
As others have noted, this sort of framing is
fraught with peril. If it must be done, it should
be done with acrylic and not with glass. Glass is
far to fragile and when sun light passes through
it, it will not warm up but the boards behind it
will. As they warm, the boards will give off moisture that has the potential for creating
condensation on the still cold glass. The other
problem is securing the back mat. Any attempt to
glue it to glazing material is likely to result in
its becoming warped, since the board will respond
to changes in R.H. differently from the glazing.
One way in which it can be secured is with stainless steel wire that is laced through holes drilled in the acrylic behind the board. The back mat can be made of two sheets, one with the wire
threaded through it and the other is glued to that. Wire is needed, since other material are likely to stretch. The wire can be secured to the
back of the backing glazing sheet with epoxy.
Most silicone adhesive cures with acetic acid.
Electrical grade silicone is alcohol curing, but
it has a very short shelf life and finding it in
a fresh enough batch is quite difficult. Beyond that, it may have other problems, as Rebecca
mentioned. Such two sided framing may be acceptable for low value, decorative items, but
valuable works should not be framed in this manner.

FrameTek makes a special extrusion that holds 2 pieces of SSB glass (or3/32 inch thick acrylic sheets) 1/4 inch apart. It was designed just for double glazing. You can check it out on our web pages - it's called FrameSpace 1/4 double. The complete assembly of glasses and FrameSpace can be bonded into the frame with any number of adhesives, including Silicone as it will be outside of the glass. I believe that no matter how you seal the frame cavity you will have condensation issues. IMHO, just because the back layer is glass or acrylic doesn't change anything much. OBTW, the plastic FrameSpace is made from is inert - test report available. It is also low carb.
Please post a picture of the finished product.

Particularly if you go with the FrameTek system.

I for one would be interested in seeing it.
Thanks for all the imput. I'm contacting customer to explain all the issues and let him decide which way to go.

I believe it best to frame in a more conservative manner with rag matting, etc.

If we do go the other way, I'll take some pix and post.

I especially appreciate the input from our conservation specialists and the willingness to share their training and experience.

Dave Makielski

"Go Amish! How about that Yoder Dame?"
Others have described the dangers of framing valuables this way. But if your customer understands the dangers and still insists, I guess it's better for you to do it better, than to send him to a less-informed framer who would do it worse. At this point it's a matter of choosing lesser evils...welcome to the Wonderful World Of Retail Framing.

First, design in as much air gap as you can. The FrameTek 1/4" FrameSpace would be perfect for most jobs like this, but I'd go for at least 3/4" (3/8" in front and behind the item); more air gap = more insulation value. (Low-carbohydrate is an excellent feature, Greg.
, but what about cholesterol & polyunsaturated fat?)

For the glazing, you mentioned Museum Glass. Good idea, but acrylic is better. Good news: With the new agreement between Tru-Vue and Cyro, we can now buy an acrylic equivalent for every Tru-Vue glass product.

Check out Tru-Vue's new "Optium Museum Acrylic", the acrylic equivalent to Museum Glass. It has the excellent UV-filtering properties of Cyro OP-3, and the anti-refelctive qualities of Tru-Vue Museum Glass.

In terms of framing glazing, it's the best of both worlds. And there's a unique bonus: It's anti-static!

To attach the undersized backer to the rear acrylic, I suggest more thickness than 4-ply. 8-ply would be better, or you could use 4mm Archival Coroplast behind your 4-ply alphacellulose board. The adhesive I'd suggest is 3M #889 double-sided tape (for attaching the board, not the art. Japanese paper hinges & starch paste are best for that, as you mentioned in your original post). 3M #889 is very thin polyester tape with a high-quality acrylic adhesive. Remember to activate the bond with burnishing or extreme pressure.