Got good ideas on how to make a good cf panel and what caul plate to use or what can be used as a tooling plate that is readily avialble?
How about an mdf board that is sealed, top coated, with gel coat ,and sanded flat?
I need panels that are 3ft X 3ft x .030 inch thickness, one side finished. I plan to vacuum infuse them with epoxy resin.
Toss up your ideas
I’ve been using steel plates as caul plates for the composite plates I’ve been making. (Lots of plates in that sentence!)
However I’ve been vacuum bagging my parts and I’m not too familiar with resin infusion so I’m not sure how steel plates would work.
why do you want to use a caul plate if you only need one side finished? I would just infuse on a large sheet of glass the cut it up to size. It would save you alot of time and grief.
Use thick tempered glass. Smooth, glossy, and needs minimal release agent.
caul plate is the secondary TOP tooling, that is used to create a better top finish (be it flat, or matched shaped tooling)
As for tooling surfaces, anything that you can coat or bag will work. If you want a long lasting plate tool, use polished metal. (Glass scares me, i’ve broken enough i nthe past!) Even plates of FR4 material can be used (has a shiney, albeit, fabric print through surface)…
If you want a caul plate for top tooling, again, aluminum, steel, anything that has release agent on it! 
I think an aluminum plate of 1/16th in. thick should be more than sufficient for your panels. I always make sure that the caul plate is properly coated with mold release agent otherwise its lot of pain to remove the caul plate from the part. Glass caul plates are good but make sure size of the glass plate is less than the size of your layup. If not, glass will brake due to uneven pressure while doing the vacuum infusion.
A glass plate would be great… some jacka** used and broke my 4ft x 5ft tempered glass i was using. He didn’t even offer to pay me for it after he broke it. Dumb jerk… i told him to wax it a minimum of 12 times before he laid up on it… nooooo some people just won’t listen to good advice no matter what.
I’ll be looking at buying another piece of glass or metal sheet/plate.
Ummm, 2 coats of wax would be plenty on glass!
I learned this the hard way. After spending all that time preparing I finally start that vacuum and experience a few seconds of relief only to hear CRACK CAKAKCARCACARCK. It’ll suffice to say I spent the next day trying to salvage my part with a sharp knife and buckets of hot water.
Glass is great and try using RAIN-X as a release agent, it works like magic with polyester, not sure about epoxy.