Will a silicone made trivet (they look like small rectangular placemats of about 1/4 inch thickness) impart any odor or chemical into the space of a pressure cooker? To duplicate the height distance of a metal trivet, two silicone trivets I saw at a store would be needed. The one advantage of using them is that they would not rust or give off any metallic odor. Some containers placed in a pressure cooker are used without a cover/lid, which causes me concern for the use of the silicone. I know that baking mats made of silicone are used and exposed to a higher temperature inside an oven, but I wondered about the different cooking environment inside a pressure cooker which utilizes steam and pressure for the cooking and didn't know how silicone would react to those factors.
Wow, I have never thought about using silicone trivets in my pressure cooker. I was told to use a couple of clean, empty tuna cans underneath the "pot." Have you had issue with a metallic odor or are you just trying to prevent it from happening? I won't try the cans if there will be a funky metallic odor or taste...
I don't understand your problems with metal trivets. I don't know what a metallic odor is. The pressure cooker itself is metallic. To hold meat (potroast, chicken) off the bottom I use the aluminum trivet that came with my old Presto. To support a metal insert (for a pudding or polenta) I use a wire rack about a inch tall. That keeps the insert above the water.
The temperature inside a pressure cooker is about 250F, well below typical baking temperatures. So I expect my silicone steamer basket would work ok, but don't recall every trying it.
I have a couple of silicone hotplates, but I never thought of using those in the pressure cooker, or in any other pot for that matter. Keep in mind that water in contact with the pan bottom turns to steam. Those bubbles will have problems escaping from under a trivet like this. Before using them under pressure, I'd suggest an open pot test. What happens when you put one in a pot of water and bring it to boil? What happens when you put the insert in there as well?
The Presto trivet is perforated, and stands off the bottom about an 1/8", so steam bubbles can escape.
No problem with metal trivets. Just that when I saw a trivet at the local "W......" store made completely of silicone, and its ease of storage, I thought that it might make for an alternative support within the cooker for another pot.
And, that its material might be innocuous/neutral.
That Ohsawa pot I read about talks about the "energetic" affect of material on food, so I thought reducing metal within the pot lent to interesting speculation on the matter!
I thought it might make for a "cushy" padding for a pot, too.
A poster's comment about bubbles possibly coming up from beneath this kind of trivet makes sense, something I hadn't thought of. Even with a 1 1/2 qt casserole dish (which I am contemplating getting as a smaller container for smaller portion sizes of rice/stews/desserts), I think of the nature of the material within the cooker. I think the casserole dish is made by Corningware and comes with both a glass and plastic cover (one for the oven, one for microwaving and refrig storage.)
I still have the question about how much space is needed around such a pot placed within a cooker! That Ohsawa pot takes up most of the space within a cooker!
"However, the turbulence makes the clay pot rattle and bang inside the cooker. To eliminate this problem, elevate the pot by setting it on the rack or trivet and adding enough water to the pressure cooker to last the length of the required cooking time. When completely elevated out of the water the inner pot heats uniformly around the entire surface of the pot including the sides and top, not just from the bottom."
A restaurant 'steamer rack' would be a good option if you can find one that fits your cooker.
Rather than a silicone trivet, I'd suggest a silicone steaming basket like these, which has little 1/2-inch legs to hold the basket up. I've used mine in a pressure cooker many times without any issues.
I have several flat silicone tivets such as you describe, but I think the expansion of the water as it heats under the large surface would easily cause the trivet to "burp" and thereby potentially dislodge whatever food you were cooking, potentially causing disasterous results.
I find the larger basket handles like the Tavola style are slightly easier to maneuver inside the cooker than the Chefn one.