It is a 1 minute job and you will only need foam/sponge (about 2cm thick) and scissors.
1.Cut a circle out of foam to match the shape of your container.
2.Place the foam circle on the sieve and screw the lid back on.
That's it! I have been carrying my pigments and powders in my handbag and they are clean and I don't need to worry about them making a mess anymore :)