Our heating plate is made of food grade 304 stainless steel. Under instructed use, there shouldn't be any chance for the stainless to oxidize and corrode.
The mineral scale is typical and harmless and it should always be white powdery looking or white film on the heating plate. If you are seeing brown spots that look like corrosion or burnt mark, the following are the possible causes.
Typically there are 3 reasons that causing these rust looking spots or burnt marks.
- The water that used to sterilize: High mineral or high chloride contain water.
a. high mineral concentration, hard water, the mineral got rusted.
b. high chloride concentration water, the stainless steel started to pit.
Prevention: Use distilled water only.
- Feeding gears weren’t not washed thoroughly, the remaining residues in the feeding gears got burnt on the heating plate. (if your heating plate gets dirty after each use, this is most likely the reason)
If there are brown spots, it's most likely there are other substances other than water that got burnt on the heating plate. These remaining substance can be the grease from the breast milk that is hard to see, grease will flow down to the heating plate during the steam sterilization cycle, and get burnt on it.
Prevention: Please make sure your clean the feeding gears with more soapy water and rinse thoroughly.
- Pitting on the heating plate. Pitting looks like small dotted rust spots.
Though citric acid and vinegar are great nontoxic cleaning agent, just like all stainless steel household pots, it does not mean to have long exposure to these strong acids. It will cause the polished surface to deteriorate over time, therefore the small pitting holes.
Prevention: Please make sure you to multiple fresh water rinse after the descaling to wash off all the remaining acid solution on the heating plate.
SOLUTIONS: Again, either limescale or brown spots can be easily clean off completely by following the descaling instruction. If the brown spot is on the edges, try adding a little more cleaning solution to immerse the edges and try cleaning the tight spots with a soft bristled brush.
If that still doesn't clean it off completely, we also recommend using "Bar Keepers Friend." This is a typical solution for server burnt on kitchen pots and pans, just remember to do multiple fresh water rinse as this cleaning detergent is a not food grade product.
How do I know what might be the cause?
Here is a good way to know which one might be the cause. First, try cleaning the heating plate back to the flawless state. Then run the auto cycle few times without any objects inside the chamber. If you start to see the brown spots, it's most likely the water is the issue. If you have changed to distilled water and you still the brown spots, then it means the object will need stronger detergent or more rinses before sterilizing.