Personally if I would make one of these I would have put the resistors in a different pattern and instead of going straight back to front and back again with the resistors that creates a rather short distance from the input to all 3 rows of resistors you make arcing more likely to reach the end of the line. using S or Z patterns with the resistors along the width of the board instead your board would only have the highest voltage at the input end and the lowest at the ground side only. that would make it take even more voltage without the risk of arc over between rows of resistors. since candle wax tend to absorb some moisture over time it would also make it even better if you potted it with epoxy. I actually managed to get my hands on a nice 100:1 probe that works well with my multimeter for HV that makes calculating much easier
Personally if I would make one of these I would have put the resistors in a different pattern and instead of going straight back to front and back again with the resistors that creates a rather short distance from the input to all 3 rows of resistors you make arcing more likely to reach the end of the line. using S or Z patterns with the resistors along the width of the board instead your board would only have the highest voltage at the input end and the lowest at the ground side only. that would make it take even more voltage without the risk of arc over between rows of resistors. since candle wax tend to absorb some moisture over time it would also make it even better if you potted it with epoxy. I actually managed to get my hands on a nice 100:1 probe that works well with my multimeter for HV that makes calculating much easier
With all due respect 10000 volts and cheap are not two words I'd like to hear in one sentence
It is a cheap multimeter though
Better to destroy a cheap multimeter than an expensive one :-)