Has anyone tried these for sighting in their thermal? Sometimes I can only get out in the middle of the day. When it’s very hot here I don’t have much of an option. Anything cold I try to put out is air temp within minutes. I can’t put targets on the ground at my range so ice bottles aren’t an option for me. Curious how well these work on a really hot day? Thanks.

https://www.empiretactical.org/thermal-flir-reflective-patches/tactical-35-x-2-inch-flir-thermal-reflective-patch-square-hookloop-5xy6e

Someone previously mentioned using aluminum foil. Sounds like a much cheaper option to me!

Plastic bag of ice?
Chemical hand warmer?

Lighter or small torch heating a nail in the bullseye?

The hand warmers work really well on cool days. It’s hitting 90 here on a regular basis right now.

A bag of ice would probably work, I was just trying to find a smaller aiming point.

I haven’t tried the aluminum foil yet, I’m not sure if it would work out on a hot day or not, I will have to try it out.

All good thoughts, thanks.

Any metal will do the same. Aluminum foil, is easy. Brass works great and is easily blackened chemically if you don't want to have a flashy surface, and it reflects the sky just as well when blackened (look at old, weathered, dark black range brass on the ground to see what I mean. It's just as obvious as shiny new brass in the thermal).
Brass is also easy to cut and shape as you wish and will stay tipped to reflect the sky toward your shooting position way better than aluminum foil when attached to a target.

I contacted a firm that makes thermal panels from a metallized plastic material. It's like a plastic tarp. Obtained a sample of imperfect, reject material they could not sell. Conducted some experiments hiding equipment from thermal detection. It works well for reflecting cold sky and would handle bullet strikes like target paper does.

Thanks for the help. I will give this a try.

someone can be the guinea pig, as I haven't done this yet, but....

get gallon size zip lock bag. fill with several layers of newspaper, about 1/4-1/2 inch thick.
wet down with water so it is wet and soggy but not sloshy wet.

lay them flat in the freezer and make a couple of sheets

to use, hang the sheet up and stick something insulated and warm in the center -

e.g. take a piece of foam like from insulating pipe or even styrofoam from the lid of a carton of eggs, wrap around a bolt, poke a hole in the center of the frozen sheet, and stick the whole assembly in the hole, using the foam to insulate the bolt so it is at a different temp.

edit - different idea -

try cutting a 2 inch square piece of flat styrofoam from an egg carton, cut a 1.5 inch square of aluminum foil, glue to the center of the foam, attach foam to center of frozen sheet.

I've used a frozen soda can in front of a cardboard box. Shows up perfectly. Just align crosshairs with the top of the can to give you a fine aiming point.

No, the above will not work, if you care about seeing where your bullet impact is.

If it's hot, get a latex glove and put an ice cube in a couple of the fingers.  Even better, staple that glove to plywood.  Plywood provides enough resistance to the bullet that a thermal impact is visible after the shot has been fired.