Check Sieves
In general, always check a sieve before using it to ensure that there is no cross contamination.
Procedure
Wipe down top and bottom of sieve with a tech wipe and ethanol.
Check for grains stuck by looking through the sieve. This is done best by using a bright background (e.g. hold up to light) in order to see grains clogging the mesh.
If there are grains, refer to cleaning methods in sieve_clean.