dnd 5e – Is there a saying that allows you to turn fabric into metal or stone?

There are no spells that turn objects into stone or metal by default. However, if you are a very good caster and have two days to work with it true polymorph should work.

Real polymorphism can turn a creature into another creature, an object into a creature, or a creature into an object. However, we try to turn an object made of cloth into another object made of stone or metal. This means that you have to use the spell twice – once to turn the fabric object into a creature, and then again to turn the creature into an object of stone or metal.

Note that the fabric object must comply with the restriction:

The item must not be carried or carried by any other creature

Since this is a 9th level spell and a wizard only gets one spell point of the 9th level per day, this means that a single wizard without throwing a free 9th time must throw it once, take a long break, and then must work again. Not ideal, but it seems to be the only way you want it.

However, it is also good to know that the effect lasts one hour after the second casting and can be stopped at any time when the concentration is discontinued. After an hour, it must be expelled.