I have made a couple hundred pot holders and I use insulbrite and some cotton batting. I never put the muslin over that.

I do the same as Sewingsuz. Have made many this way. Don't know if there is a better way but this works for me.

I've made umpteen dozen casserole carriers and cast iron handle covers now using insul-bright. I can definitely see a difference in sides. Cotton fabric, thin fusible batting, insul-bright, thin fusible batting, cotton fabric. Shiniest side toward the item you want to keep hot/cold. So for a table runner to protect your table I would guess shiniest side up, leaving more batting/protection between the hot item and table. I'm not quite sure how the muslin would help with condensation as it's not going to 'waterproof' anything. I can't imagine you would have that much condensation on a table runner anyway.

The potholders I have made that I like the best are the ones that I used insulbrite , cotton batting, and another layer of insulbrite. Makes the holder very puffy but I like that.

I always use old towels for batting on my potholders. One towel makes lots of potholders.

I do also. Been doing that for years...

I'm with elly66, when I make a hot pad, I use two layers of insulbrite. I don't think condensation is a problem. There is no condensation when using cotton batting and fabrics with it. I usually have a quilted side, insulbrite, batting, insulbrite, and a back. But then I'm making hot pads for my kitchen island where I know I will have oven hot pans. So I want it thick and sturdy.

I have used insulbright a lot in potholders and never have heard complaints that they were unusable because they got too hot. I don't pay much attention to right side and wrong side because most pot holders get used with either side being the right side. In some I have put an extra layer of batting and others not. I have small hands so I don't like my potholders to be too thick as they are clumsy in my hands. I use potholders for trivets on the table and haven't noticed any problem with condensation.

I used insulbrite in a Holiday table topper for my neighbor. It was double sided for Thanksgiving and Christmas. It did the crinkle sounds but it worked perfectly to prevent any further burn marks on her solid oak table. She said that her table was warm not hot! I guess that is a success! I do plan to longarm another one for myself.

I'm glad I am not the only one. I wanted to make a pair of potholders. I was told at the quilt store all I needed was insulbright instead of batting in my project. I was so dubious I asked twice! Well these pot holders suck! There is not enough insulation and the mitts get hot. What a waste of time and money! Glad I only made one pair.