I'm about to open up a working Krielser 11-81a to check parts and probably replace filter caps etc. Looking through the back panel, the valves seem to have some kind of white dried crusty substance on them. I guess it could just be dust and general 50 year old crud, but I thought it important to check with those familiar with these radios whether I could expect any asbestos shielding, and if so how I should proceed. I'd rather know before I unscrew anything. Thanks...

Although asbestos was sometimes used as a heat shield above the valves in vintage radios, they tended to be earlier than the 11-81.

Here's a photo of the inside:

https://www.radiomuseum.org/images/radio/Kriesler_radio/11_81_1079672.jpg

I've never seen any asbestos inside plastic radios however this doesn't mean it's not there. My guess is that your radio has just collected dust over time and this is typical of most valve radios as they required ventilation to get rid of heat and mains powered radio valves give off lots of heat, especially the rectifier and power amplifier valves.

One thing we all need to remember though is that when valve radios were relegated out of the household and into garages and workshops, this is where it is possible for them to accumulate dust that contains more than clothing fibres. Millions of cars on our roads are still fitted with brake pads and shoes that are made of asbestos. If you live near a main road or side street speed humps the dust from these brake pads can travel through the air and it ends up everywhere.

Then there is the issue of what the space in the garage or workshop was used for. If it was used for cutting fibro, any product made of a ceramic fibre or silica then there is a good chance a radio will have 'collected a sample' from the surrounding air.

As a precaution and right from the outset in my early days of collecting, I have always cleaned radios outside with the wind coming from behind my back. That way any dust, poisonous or not, doesn't end up in my lungs. I am very fortunate in a way - I've always worked around these hazardous substances in my roles as an electrician or building manager yet chest x-rays a year or two ago showed that I'm clean.

My response was a loud "thank f----- c-----". Use your imagination to complete the guessing competition because the rules forbid me completing it here. The reason for that reaction was that it's been about 30 years since I started working and that is the general 'gestation' period for asbestosis.

Thank you everyone for your input. There was a piece of asbestos shielding in my Kriesler 11-104 Multisonic console unit from 1968, but it looks like there's none present in the 11-81. I'll take Brad's advice and open it up outside for the first time. Better to be cautious with these things