The Demon Glass comes in a generous supply of a 1 litre bottle, which provides one of the best values of the products we tested. The easy to understand instructions on the rear of the bottle remind you to shake well before use, and to use two microfibre towels to buff and dry. However without lubrication properties in the ingredients [more on that later] to lift the dirt, it neglects to say that it would be advisable to pre-wash the windows before risking swirl marks caused by the need to buff on heavily soiled windows. 

With that said, we found the cleaning properties to be adequate, and bar a few stubborn marks from bird droppings, the CarPlan Demon Glass left the window clear. Partial smears needed to be reapplied and buffed out, which was tiring considering the test area. The best in class cleaners provide an easier time, with less effort, but that is to be expected at this value price point. The bottle did not leak during our storage and shake test, and was happy to rest horizontally and under light compression. The bottle comes with a very wide spray pattern which made the external part of the cleaning test easier but the spread feels a little too wide to maintain any control during the interior test. This is something to bare in mind considering the close proximity and potential toxic ingredients when cleaning in such an enclosed space. It is preferable to avoid runs when cleaning interior windows, and the wide spray made this difficult. 

We think the Demon Glass is best used as an external window cleaner, despite its claim as a 2-in-1 mist prevention. We did not notice any significant difference in anti-mist performance versus the other window cleaners. However it is important to note that the anti-misting properties were not the focal point of the test, as it was conducted during June 2024, and therefore we were unable to record a reliable judgement or fair comparison. Overall, CarPlan Demon Glass provides a decent cleaner in a package priced to good value, however there were better performing cleaners in this price range and above, so it falls short of being awarded a FritzReview recommendation.