I made a horrible mess of a pyrex dish on Sunday by roasting turnips. Olive oil has been baked onto the dish forming an almost rubberized coating and there are stains from the turnip that I can't get out. I've tried soaking, a nylon scrubber and baking soda.
Any ideas would be gratefully appreciated as this is one of my favourite dishes and I would like to save it if possible.
Usually, a standard approach is to work between a basic solution and an acidic solution -- alternating them. Baking soda will provide the basic solution. If you find it does very litte, then you can then try soaking the Pyrex dish in white vineager or Bar Keeper Friend solution (one or the other, not together). My guess is that basic solution will work better in your case, but it never hurt to try.
Another thing which will help is to heat up the solution. Pour in your baking soda solution, white vineager, or Bar Keeper Friend solution, and put the dish in the oven to warm it up to say 250-300 oF. This will help. Now, you don't want to put anything which will produce toxic fume under heat.
If neither is working, then you can move to more aggressive method like an oven cleaner or something.
Don't feel badly. That always happens when cooking in Pyrex. Fats, especially spray-oils, leave that rust color residue.
What I do is pour hot water in it, let it stand for a good hour, then use good old fashioned SOS pads and a lot of elbow grease. My Mom's Pyrex is 30 years old and still looks like new because she does this every time she uses it.
A pain, I know, but it'll keep your Pyrex looking good for years.
Just moisten it and put in some dishwashing (machine) soap. Let it sit. It should come off easily with a nylon scrubber. I've done it before.
Whatever you do, dont use anything which will scratch it. Pyrex is tempered glass, so has internal tension. This can cause imperfections, even small ones, to propagate. The additional stress of temperature changes can cause sudden failure.
I would soak it in diluted ammonia, which should loosen everything, then rinse and scrub with no abrasives of any kind.