All Vorwerk products meet exceptionally high quality standards, and the Thermomix ® is made of premium stainless steel that is very resistant to discolouration resulting from oxidation. It is very unlikely that your Thermomix® bowl will become discoloured, but not impossible.
The mixing bowl may become discoloured for the following reasons:
- If the mixing bowl is not cleaned and rinsed according to the instruction manual.
- If the mixing bowl is not rinsed before it is put in the dishwasher (not recommended in the instruction manual). Please rinse the mixing bowl before putting it in the dishwasher to remove all food residue or alternatively, start the dishwasher’s rinse cycle if the dishwasher does not need to be started immediately.
- If the mixing bowl is put into the dishwasher with the still knife attached (not recommended in the instruction manual). Please remove the knife before putting the mixing bowl in the dishwasher. However, floating rust in your dishwasher may also cause discolouration. In this case, please remove the floating rust in your dishwasher by using citric acid powder or dishwasher cleaner. Put the citric acid powder or dishwasher cleaner in the detergent dispenser and start the intensive cycle. When the cycle has finished, leave the door open until the inside of the dishwasher is completely dry. The stainless steel may also discolour if the mixing bowl cannot dry properly. Please make sure that the mixing bowl is completely dry before assembling it again. If necessary, use a soft dry cloth to dry the contact pins AND the edges of the hole in the bottom of the mixing bowl, as these are not made from stainless steel and can therefore rust.
- Stainless steel features a protective chromium oxide layer on its surface. If this protective layer is damaged, e.g. if gets scratched by a knife, oxygen from the surrounding environment will immediately form a new protective layer. However, some substances can damage and break through the protective layer without allowing it to regenerate. Furthermore, if this protective layer is scratched by sharp objects, it may lead to oxidation. If a recipe uses acidic foods such as salt, lemon, vinegar, ketchup and mayonnaise, please make sure you clean and dry the bowl thoroughly immediately after you have finished cooking.
- Other metallic cleaning materials (such as steel wool) may scratch the stainless steel bowl and make it more susceptible to discolouration and rust. This is also true for other metal kitchen utensils, so please do not scrape the bowl with metal objects such as spoons or knives. Use the spatula instead.
- Over a prolonged period of time, salt and water can damage the stainless steel. This is why you should avoid storing cooked dishes in the mixing bowl, and clean and thoroughly dry the bowl, knife and seal after use.
- When steaming food, minerals dissolved in the water, especially limescale, remain in the bowl. As stated above, the bowl, knife and seal need to be cleaned and dried thoroughly after you have finished cooking.
- When cooking starchy foods, such as potatoes or noodles, the mixing bowl may become discoloured. This has nothing to do with corrosion, it is just discolouration. To remove this discolouration, fill the mixing bowl with 1.5 litres of water and add a dishwasher tablet. Heat it to 70°C for 60 minutes on speed three. Afterwards, pour away the cleaning solution and remove any remaining discolouration with a stainless steel cleaner. Rinse the mixing bowl thoroughly with water and dry.
Thoroughly cleaning the bowl should remove most discolouration. Liquid stainless steel cleaners and pads can also be helpful. However, it is important make sure that the cleaner is suitable for stainless steel.
Cleaning the bowl with a vinegar solution can also help. To do this, mix 1 L of vinegar (or 250 ml vinegar essence and 750 ml water) with ¼ teaspoon of detergent, pour this into the bowl and mix the solution on level one at 50°C. Leave the solution to work for at least one hour – or even overnight. Rinse the bowl thoroughly with clean water and make sure it is completely dry.