Help! Simple but difficult way to semi stick reflective mylar to sheet metal

Wow, the whole question fit in the Topic line!  Amazing!

Well, anyway, we're in the process of finalizing a design for a solar hot water heater and are still trying to figure out a good/better way to stick our mylar to our sheet metal.  The sheet is about 10 ft. (sorry about that old fashioned non-metic system usage, but we're on the U.S.-Mexican border and most of the things here in Mexico are still measured in the old system - sigh) by about 4 ft.

We have used axle grease - it's o.k. but hard to spread and to make into a VERY thin film.  If the film is not thin bulges appear in the mylar since itself is only about 2 mil thick.  It was good, on the other hand, because it allowed us to position the film correctly on the metal sheet...

So, this time we tried silicone - out of a spray can.  It also seems to be good, perhaps a little better since we can spread it with a small paint roller but after several days it's not holding the mylar down well enought (which is probably to be expected since we're using silicone and it's not really sticky).

So, we need something which will allow us to position the film (slippery) while being a very, tiny, wee, itsy bitsy sticky in the long run.  It cannot of course be anything biodegradable - like honey - yuck - for obvious reasons (it's going to be in the sun and eventually it will, biodegrade, into who knows what).

Maybe silicone and ... Elmer's glue???  We're stuck.  And, after googleing till our eyes have dropped out, we can't find any reflective mylar with a sticky backing.  What the heck do they stick on those window tinting sheets???

Anyway, any help would be greatly appreciated and of course, Have a wonderful afternoon!  :)

kelseymh1 year ago
As a follow up to my initial process recommendation...

I know you said you wanted to be able to "position the film", but that is going to get you into trouble in the long run. If the Mylar is not held firmly in place, then any contact with the surface will create wrinkles, or worse, tears in the material. You really do want to glue the Mylar down (even if you don't know that's what you want :-), in such a way that you don't leave permanent wrinkles or bubbles.
kelseymh1 year ago
A spray adhesive is the right choice, such as a photo-mounting adhesive like 3M Spray-Mount or Super 77.

With sheet metal, you need the surface to be very clean, very dry, and very smooth. Wash with mild detergent and water to remove dirt, grime and grease. Wear powder-free gloves (latex or non-latex as you wish) for the rest of the process, to avoid depositing finger oils. Go over the surface with non-soapy steel wool to get rid of any rust spots (even tiny ones). Brush and blow the surface to get rid of as much dust and grit from the steel wool as possible. Use rubbing alcohol and non-linting wipes (such as Kim Wipes or tissue paper) to clean the surface. Repeat as necessary until you have a clean, polished surface.

Spray the adhesive onto the metal surface, in a well-ventilated room. Put the Mylar down along one edge, maybe 10-15 cm, overhanging all sides, and use a firm roller (not for paint, but rather a hard rubber inking roller) to ensure that the Mylar is completely smooth. Lay down another 10-15 cm and roller it out smooth again. Repeat until you have covered the metal surface, and hopefully have excess Mylar all around. Keep the Mylar sheet under a bit of tension (not too much) throughout the process to avoid wrinkles.

Follow the adhesive directions for curing, to ensure that it is completely dry. Once dry, use a sharp blade (scalpel or box cutter), to trim the excess Mylar. Alternatively, you can flip over the metal plate and adhere the excess Mylar to the back side. That will reduce the chance of tearing or delamination.
+10 :-)