Cleaning sauna stones

Rinse them, brush them, dry them. That's the whole job. The trick is doing it with the heater cold and not putting wet stones back.

Which stones need it

HUUM says to clean stones that are dusty or covered with residue from iron-rich water¹. Harvia says re-stacking is a good time to clean dust and debris off the stones².

Dust isn't just untidy. HUUM says stone fragments and dust that build up inside the heater restrict airflow³.

Step by step

Follow your heater's manual for your own model. These steps come from the two makers' guides.

1. Switch the heater off and let it cool. Harvia says to ensure it's cool and turned off before maintenance⁴. Then take the stones out.
2. Clear the heater. Remove the stone dust and fragments from inside it³.
3. Rinse. HUUM says to rinse under running water¹.
4. Scrub. HUUM says to gently shake or scrub off residue¹. Harvia suggests warm water and a soft brush².
5. Dry. HUUM says to let them dry completely before placing them¹. Harvia says the same: wash, and allow the stones to dry before restacking⁴.

New stones need washing too

Fresh from the box doesn't mean clean. HUUM says washing stones before their first use is a must-do¹. Harvia says to start piling by washing the dust off the stones before they go into the heater⁵.

That applies even if the box says pre-washed. Harvia describes its own stones as pre-washed, and still gives the washing advice⁵.

How often

Cleaning goes with the yearly check. Harvia says to maintain stones at least once a year, and more often if you notice stone residue or small pieces of stone on the floor under the heater⁴. HUUM lists excessive stone dust as a sign to inspect the stones³.

What not to bother cleaning

Cleaning won't fix a damaged stone. Harvia says to discard stones that crumble or are discoloured⁴. In its summer maintenance guide it also says crumbling or yellowed stones should be replaced².

So sort as you go. Clean the sound ones. Bin the rest. The replacement page lists the signs.

A few practical notes

• Do the job over a tarp or a bucket. Water and stone dust go everywhere.
• Don't hurry the drying. Both makers say to let the stones dry before they go back.
• Once the stones are dry and the heater is clear, load them as the loading page describes, with air gaps left.
• Wood-fired stoves follow the maker's manual and your local fire rules, and they need a vented room because of carbon monoxide.