Following along the bifilm thread and trying different things made me realize I don't know how much porosity I'm getting. Sanding and filing was showing some but I realize without a microscope you'll never see it. I read where 1,000X magnification may be appropriate, and I found a cheap ($16) microscope which claimed to do 1,600X. Plus, it is all electronic and uses a computer screen for a monitor. I received it today and looked at three pieces. I don't have polishing paste yet so I had to rely on sandpaper i had, 1,200 grit. Left is an engine box section, center is a solid suspension component, and right is a manifold I cast using a square pouring basin and inlet riser. Here's what the gate and riser looked like on the manifold The microscope came with a clear standard or calibration card. Here are three pictures against my table cloth. The standard does have specks all over it, this is the 0.03 MM line 0.05 MM 0.07 MM I think the 0.07 MM image is a little more magnification. I intended to not change the setting but think I did looking at the picture. The box section has lots of porosity. Here is one close to the edge, with the 0.07 MM line The suspension part seems clean, here are some of it's inclusions The dimple in the center of the top of the manifold part is still visible Here it is under magnification, it physically measures about 1-1/2 MM. Here are some other inclusions on the top of the manifold. This was at the top of the casting. The inlet end of the manifold was pretty clean, compared to the commercial castings. Here is one inclusion I found. I hope to get some better pictures when I get the polishing compound. I was pretty please with these. I think the table cloth photos show the camera does a fair job. Comments?