Some of the best things to mix HXTAL in would be glass jars. This is sometimes difficult when trying to weigh out your HXTAL though since glass jars generally weigh too much for smaller scales to handle both the jar and the HXTAL mixture.
We do offer chemically inert plastic cups in both 1 ounce and 8 ounce varieties for mixing your HXTAL in.
If you do use your own plastic cups, please make sure that they are chemically inert as any active chemical (such as freshly mixed HXTAL) will have a tendency to interact with plastics and leach material into the mixture providing unwanted results in your bond joints (often showing up as bond failures or an inability of the epoxy to fully cure).
A good way to test your plastic cups is to put some acetone in the cup and let it sit overnight. If the plastic is discolored by the acetone, then the chemicals in the cup are not inert and you should not use it to mix your HXTAL.