Well, @Coal Fired Bricks on a Flickr comment did say that he will be doing resin casting. I checked out the type of resin he is using and it is food grade impact resistant.
Here is some info on it
TASK® 11 urethane casting resin is a semi-rigid plastic (has some flexibility) that is strong and very tough. Originally developed for high impact tooling (drop hammer punch), TASK® 11 also offers good abrasion and chemical resistance and is ideal for a variety of industrial applications.
This product is suitable for some FDA/USDA applications - dry food contact only.
TASK® 11 applications include making abrasion resistant parts, foundry patterns, encapsulation, roller facings, metal bonding and vibration pads
Not sure what he may be using for molds but if using silicone he can make a rail shape.
@slide_potentiometer yes the inside part would have to be thin, not sure how that could be fixed strength-wise.
Here is the Flickr link https://www.flickr.com/photos/188099743@N07/49912714948/in/dateposted-public/
@Coal Fired Bricks do you know what you may be doing for a realilistic shape?