I don't make pot holders and probably won't. I think if I would, I would try 2 layers of insulbrite and put batting between them.

I have some that are years old, stained and worn but I still use them. The thick aluminium foil was used not the wimpy kind. I think the heavy foil available now two layers may have to be used. It certainly isn't as heavy duty as it use to be.

I use recycled jeans. I put a layer of jean fabric between two cotton battings. ....works great, and the price is right

I usually use two pcs of warm and natural and one of insulbrite. Works for me, but if I am ot od insulbrite I use three pcs of batting. I found that two pcs of batting didn't shield from the heat very good. My machine has no problems sewing through all this, it is a Elna 740. Sews through like butter. I also use a walking foot. I have found it hard to get insulbrite around here for a while, as soon as I fund it I am gong to buy a lot, lol.

I use warm and natural. I put a sleeve on the back and insert a silicone pot holder. It can be used for pots and on the table for hot dishes. I coordinate them with the seasons. They are very versatile. They are easily changed from mat to mat.

I don't understand the need for that much padding in a potholder. We're not talking molten pig-iron here. LOL
If you use thin stuff like warm and natural, another layer probably would be needed, but regular high loft batting and even low loft, even one layer is sufficient.

I made one of those bowl holders that asks for two layers of batt. I used only one, of polyester, and it works just fine. I've used it multiple times. I've never seen polyester melt. Maybe it would if you left the iron on it long enough to scorch.

My favorite pot holders are just two layers of old Turkish towel. (It was a nice heavy towel.) Never need more than one. I should cover them with some pretty fabric, but I'm too busy using them to take the time.

it may be a bit much as far as gripping with it. I have used 1 layer of jeans (recycled) fabric and one of batting. for handling a roaster coming out of a 450 degree oven I think I would want either the insulbrite or 2 layers of batting with denim in the center. like someone said-try it. potholders are small enough that you won't be out much if it is not enough.

I, too, use older wash cloths and used towels for inside my potholders. I'm recyling and saving at the same time. IMHO.....using three layers of batting would make a very heatproff pot holder but I would make it a little larger than normal to adjust for the bulkiness.

Why not take the layers you want to use, pin all together with the fabric on the outside, and do a test next time you bake something. Could try using different ways with different battings- when you get the right method for you, sew them together, and the of course share what worked best here on the board.