Why is there a film on my dishes after using the Pure-Castile Liquid Soap?Updated a year ago

This residue is most likely a reaction between the Pure-Castile Soap and the minerals in your water. This is completely normal and can easily be cleaned with the right products.
 
If you have hard water, it is more likely that you can encounter some mineral build-up. The interaction of hard water, and even soft water, with any true soap (not synthetic detergent-based soaps), can leave behind a thin film of minerals that appears as residue or “soap scum.”
 
Hard water contains dissolved minerals in the form of calcium and magnesium. All true soaps, such as castile soap, will react with these minerals to form insoluble stearates, which are visible as a whitish precipitate. This effect can interfere with foaming capabilities and may leave soap scum on surfaces. This whitish precipitate builds up primarily on surfaces where water is left to dry, such as in sinks and showers. It is not an issue on floors, counters, or other hard surfaces where the castile soap is diluted for cleaning and standing water is mopped or wiped up.
 
You can easily dissolve residue left from our soap with vinegar by diluting one cup (240 mL) of vinegar in a quart (1 L) of water and spraying it on the affected surfaces. Let it sit for about 5 minutes (not long enough for it to dry), and then rinse it away with very hot water. If this residue is really thick, you may have to do this again or use a stronger concentration of vinegar. 
 
Additionally, a mild detergent like our Sal Suds Biodegradable Cleaner is great at cleaning any residue off a shower or surface. You can scrub the residue off with this product, and for really stubborn areas, sprinkle baking soda for extra help!
 
For more information on this subject, we encourage you to check out Lisa Bronner's blog, Going Green with Lisa Bronner. Most notably her posts The Chemistry of Water and Using Soap to Test for Hard Water.