My colleague commented that I have an old classic keyboard which I like very much. However, the only problem was the dirt accumulated over the years. After trying to clean it with a damp tissue paper, I was not the least happy because it was still very dirty. Then an idea came that I should try to wash it!
So I flipped over the keyboard and found a series of screws that I could remove. The rest is now history. I wash the keyboard under running water and what surprised me was that the dirt drop off so easily.
If you try it, please note that I am not responsible to any damage that may happen to your keyboard. Do use your common sense.
The other side of my keyboard has NO electronic. So it is safe to wash. But there are parts that may drop off.
The keyboard has one layer of soft plastic "key". Be careful not to damage this.