I can give you several sentences.
I/you/we/they stiffen. He/she/it stiffens.
Loosen up is the opposite of stiffen up.
To stiffen fabric for outdoor use effectively, you can use a fabric stiffener spray or a mixture of water and white glue. Simply spray or brush the stiffener onto the fabric, then allow it to dry completely. This will help the fabric maintain its shape and durability when used outdoors.
To stiffen a leather bag, you can use a leather stiffening spray or apply a leather stiffening solution to the inside of the bag. Make sure to follow the product instructions carefully to achieve the desired stiffness.
The rubber gaskets are usually pliant but stiffen in very cold temperatures. (metaphor) The pliant minds of the children accepted the sea captain's tall tales as true stories.
Use a heavier weight
lack of potassium
they clean the insides of the body then they use this pacific kind of liquid to stiffen the body and rap cloth around the body.
stiff
set, solidify, stiffen, :)
i do not know how to use embalming in a sentence. (there is the sentence)
the molecues stiffen up