Yes, it is generally true that vacuum insulated cups or bottles can be ruined in the dishwasher. Most vacuum insulated cups are made from stainless steel and have a double-wall construction with a vacuum-sealed gap between the inner and outer walls. The vacuum insulation is what helps to keep beverages hot or cold for an extended period.
Dishwashers use hot water, strong detergents, and high-pressure jets to clean dishes, and these conditions can be harsh on vacuum insulated cups for several reasons:
Temperature: The high heat of the dishwasher can affect the vacuum seal, causing it to break or weaken. This can result in the loss of insulation properties, making the cup less effective at keeping beverages hot or cold.
Detergents: Some dishwasher detergents may contain harsh chemicals that can corrode or damage the stainless steel finish of the cup.
Water pressure: The high-pressure jets in dishwashers can force water into the vacuum-sealed gap between the walls, disrupting the vacuum and leading to potential leaks.
Coatings: Some vacuum insulated cups have special coatings or finishes that could be damaged by the dishwasher's cleaning process.
To preserve the quality and insulation capabilities of your vacuum insulated cup, it is generally recommended to hand wash it instead. Hand washing with mild soap and warm water is gentler on the cup and helps to maintain its performance over time. Additionally, avoid using abrasive sponges or brushes that could scratch the surface.
Always refer to the manufacturer's instructions for specific cleaning recommendations for your vacuum insulated cup, as there might be variations in materials and construction that could influence the dishwasher's suitability.