The easiest way to do this is to freeze the plasticine. To do this, just keep the trousers in the freezer for a while until the plasticine hardens.
After this, it will be easy to remove it with the blunt side of a knife or other suitable object.
In this case, use baking soda. An alkaline substance based on sodium bicarbonate penetrates the fabric fibers and dissolves dirt.
The component quickly becomes active, but to completely remove the stain you need to rub in the soda with a brush; it will take time for the components to break down.
You can use a hairdryer instead of an iron. The plasticine will melt under the influence of high temperature and be absorbed into the napkin.
If a small stain remains, you can wipe it with acetone, ammonia or gasoline.
An ice cube can also be very effective.
Pour 100 ml of water into a glass; Add a few drops of peroxide and ammonia, mix; Soak a cotton pad in the liquid and begin wiping the damaged area.
In a few minutes you will be able to remove the plasticine from your clothes - all you have to do is wash the item in the usual way.