Mis-adventures in casting

To have a Chicago themed layout, one needs apartment buildings, two flats and three flats. And with these buildings come lots of windows. Lots and lots of windows.


So, to "aid' in construction, I have started to attempt to cast my own windows. I made masters of various styles and made some molds.


Alas, I have lots and lots, and some more, of air bubbles in my castings. I've tried pouring slowing, shaking the table with an orbital sanders, pouring quickly, but to no avail. I still get voids, bubbles and pin holes. 


I know what the answer is: to use a pressure pot. I'm just just sure I want to make that big of an investment in the casting to get that. I'm going to ask some pros who have more experience than me and see what happens.


I've started constructing the basic Chicago two flat, with cast windows with lots of pin holes and air bubbles:

This is the front of a 2 story, 2 flat. It will be a three sided bay window with a recessed door on the right side.


Unfortunately BJ Traction's two flats are no more and DSL Shops' two flats are in S scale. So, scratchbuild it is.