JO, I collect about a liter of ash/char from the ashpit (cleaned every ~ 500km) and two cups of pure ash in the cyclone after every 200 km.
Everything after that is a minority. I clean the hot filter every about 1000 km but it wuldnt be nessesery. Most of the soot just falls down from the fabric when it colects enough. But interasting, there is only charcoal dust on the hotfilter. Black as black culd bee.
I only end with trace amounts of soot after the filter. Just to paint the components the nice black colors
TomC, a hot filter is a system when the gas gets filtred just after the cyclone and then gets cooled clean. The obvious advantige is you never get soot in the cooling rails.