OK, once the fiberglass seat base in done, the foam process begins. This is what a mold looks like before it is closed. You can see the shape the foam will take in the red area of the mold.
Next, a test shot is done to look at the foam to verify the chemical mixture is correct. This is done regularly for quality control purposes.
The foam starts as a multi-part liquid fed individually into a mixing nozzle, when combined through the mixing nozzle the resultant chemical mix foams (and grows) like mad! You can see the before and after in the following photos.
Each seat receives a specific foam "shot size". When the mold is opened, this is what a seat looks like:
