Advice on asbestos in a 1930's radio. - UK Vintage Radio Repair and Restoration Discussion Forum

MurphyNut · 24th Sep 2018, 8:42 pm

My latest radio that I'll be working on soon is a Pilot U225 from the mid 1930's.
I picked it up rather cheaply maybe because it contains a sizable sheet of asbestos, I must admit not noticing this when I purchased it.
Unusually this sheet is situated on the underside of the top of the cabinet to protect it from the heat from the mains dropper. (see picture)
I was wondering what I should do about this before I take out the chassis , it's quite fragile and if you touch it it will leave a white deposit on your finger. I was thinking perhaps sealing it with PVA sealant.
Any thoughts?

The Philpott · 24th Sep 2018, 8:54 pm

That's what i would do. Frustratingly i have been unable to untangle from data sheets on PVA, how it will age under influence of heat.

Andrewausfa · 24th Sep 2018, 9:21 pm

Hi Clive

I had some in a radio and just painted it white with thick water based acrylic. Yours is substanially larger than my bit though. PVA will just go brown I bet.

A very nice looking set that Pilot, good luck with it.

Andrew

P.S. from the Bostik UK site re: Asbestos encapsulation: 'The 30-17 PVA sealer will permeate the materials and seal in any random fibres. Our protective sealer coatings can then be applied by brush or airless spray, resulting in a dried film that is flexible, durable and resistant to fire, water, mould and insect attack.' Doesn't mention heat from droppers in 70 year old radios though oddly.

turretslug · 24th Sep 2018, 9:31 pm

I'm in no way any sort of expert on asbestos handling, but I would be inclined to gently but thoroughly water-mist the asbestos part (using a trivial-cost horticultural-use spray bottle from a DIY shed, and having shielded the wood/electronics with polythene sheet) before applying the PVA- this will reduce the amount of dust when handling and brushing PVA, and will help the PVA penetrate and bind.

If anyone has better/more informed advice, it would be good to hear but I fear that consulted expert authority might go a bit doctrinaire on "proper disposal" and so on. I'd also take it for granted that if the stuff shows up on finger touch, then the chassis ought to be cleaned outside with care over keeping the face away from the dust.

Radio_Dave · 24th Sep 2018, 9:47 pm

I wouldn't paint anything on asbestos that wasn't specially designed for that purpose.

If something you paint on it shrinks or peels off it's going to free fibres as it does so

.

Regards
David

Phil G4SPZ · 24th Sep 2018, 9:51 pm

I understand that PVA can be diluted in water and then applied using a sprayer. Once dry, perhaps a heat-resisting automotive paint designed for exhausts etc could be applied.

It does seem to be a huge sheet of material, when the heat rising from the dropper would be concentrated in one small spot, as evidenced by the dark mark above the resistor. I wonder if the sheet is original? An odd bit of design, too; you'd think placing the dropper lower down in the cabinet would have enabled a metal heat shield to be used, to duct the heat safely away from the cabinet top and out of the ventilation slots in the back, as in some round Ekcos.

Andrewausfa · 24th Sep 2018, 10:12 pm

Quote:

Originally Posted by Radio_Dave

I wouldn't paint anything on asbestos that wasn't specially designed for that purpose.

If something you paint on it shrinks or peels off it's going to free fibres as it does so

.

Regards
David

It hasn't. And I'd suggest the stuff that is specifically designed comes in 10 litre barrels for industrial encapsulation and is mighty expensive.

Andrew

MurphyNut · 25th Sep 2018, 10:20 am

Many thanks for the responses, Looks like sealing it with PVA and perhaps a coat of white heat resistant paint on top of that.
I'll certainly feel happier having the Asbestos stabilized before spending time on the cabinet.
Yes Andrew, it's a nice looking set and will I'm sure respond to a bit of TLC.

dave walsh · 25th Sep 2018, 1:38 pm

You'll have to seal it with something Clive whatever you decide to do. It doesn't look very original to me so I'd be inclined to seal and remove. A scrap of Aluminium as a heat shield would probaly be more in period anyway. There may also be an alternative low temperature voltage drop solution that could be employed while leaving the original dropper in place perhaps. Have you created any more of your amusing 1930's style video demonstrating the collection?

Dave

MurphyNut · 25th Sep 2018, 1:44 pm

Quote:

Originally Posted by dave walsh

Have you created any more of your amusing 1930's style video demonstrating the collection?

Dave

Not recently, But I have a few new Murphys that didn't feature in "Murphy Madness" so I feel a new movie coming on at some stage.

PJL · 25th Sep 2018, 1:54 pm

Quote:

Originally Posted by dave walsh

You'll have to seal it with something Clive whatever you decide to do. It doesn't look very original to me so I'd be inclined to seal and remove.
Dave

I agree, seal by soaking in PVA and remove. Do any work on it outside with a mask and ideally disposable overalls. Wash the chassis and cabinet down after removal and dispose of any materials used. Strictly you should double bag the asbestos and cloths/materials you have used and take to a household waste facility. If you are really neurotic like me, you could varnish the inside of the cabinet.

Nickthedentist · 25th Sep 2018, 2:37 pm

I agree. I'm not too concerned about asbestos in radios, but that is a bit special!

I'd remove it, and replace with something else and possibly do what Dave says and get rid of the dropper somehow.

I would certainly be willing to sacrifice any authenticity in this instance.

Nick.

dseymo1 · 25th Sep 2018, 4:42 pm

I don't think PVA would be suitable for treating the asbestos should you decide to keep it in situ. PVA can be applied to sheet material, allowed to cure, then re-activated in the manner of a hot-melt adhesive using a smoothing iron. Clearly, that sort of re-activation is not desirable here.

kalee20 · 25th Sep 2018, 5:22 pm

It does look rather horrid design!

Asbestos is an ideal material here - heat resistant, good thermal insulator. It will neither conduct heat to the wood of the cabinet, nor degrade itself at its hot spot.

Thick aluminium as a shield will of course conduct heat from one side to the other rather well - but it'll also spread the heat out. So, you will have a warm-all-over cabinet top, rather than one which is hot at one particular spot.

I share the misgivings of others about use of diluted PVA to an extent - it will degrade with the heat. But, I tend to think that the heat will be concentrated in one spot mainly, which is towards the middle of the sheet. So if you spray or soak the whole thing with PVA, the friable edges will stay intact, and the hot-spot (which looks as though it would stay relatively intact), if it loses its PVA there, will matter rather less.

Personally I would re-site the dropper, mount it lower down, and horizontal. After all, that's what the Pilot designers probably had in mind all the time, they were just cut short and the radio rushed into Production before it was quite ready!

julie_m · 25th Sep 2018, 11:14 pm

Forum member Ed Dinning has made autotransformers for the Bush DAC90, that reduce heat output considerably. Could you fit something like that in your Pilot?

Yarraman · 25th Sep 2018, 11:29 pm

How about spraying the Asbestos with "VHT Paint" the type car mechanics use to spray manifolds ?

Radiocruncher · 26th Sep 2018, 8:26 am

Have a look at this thread that went pretty deep into the subject https://www.vintage-radio.net/forum/...d.php?t=144002

Regards

Graham

chriswood1900 · 26th Sep 2018, 8:46 am

When faced with a similair problem I safely disposed of the asbestos and used Superlux which has a very similair apperance see this site for details:-
https://www.fireboards.co.uk/?gclid=...SAAEgJB0_D_BwE
You should be able to get it from a local builders merchant.
Chris

24th Sep 2018, 8:42 pm	#1
MurphyNut Heptode Join Date: Apr 2016 Location: Croxley Green, Hertfordshire, UK. Posts: 979	Advice on asbestos in a 1930's radio. My latest radio that I'll be working on soon is a Pilot U225 from the mid 1930's. I picked it up rather cheaply maybe because it contains a sizable sheet of asbestos, I must admit not noticing this when I purchased it. Unusually this sheet is situated on the underside of the top of the cabinet to protect it from the heat from the mains dropper. (see picture) I was wondering what I should do about this before I take out the chassis , it's quite fragile and if you touch it it will leave a white deposit on your finger. I was thinking perhaps sealing it with PVA sealant. Any thoughts? Attached Thumbnails __________________ Clive

24th Sep 2018, 8:54 pm	#2
The Philpott Dekatron Join Date: Aug 2016 Location: Colchester, Essex, UK. Posts: 4,107	Re: Advice on asbestos in a 1930's radio. That's what i would do. Frustratingly i have been unable to untangle from data sheets on PVA, how it will age under influence of heat.

24th Sep 2018, 9:21 pm	#3
Andrewausfa Octode Join Date: Dec 2010 Location: St Ives, Cambridgeshire, UK. Posts: 1,180	Re: Advice on asbestos in a 1930's radio. Hi Clive I had some in a radio and just painted it white with thick water based acrylic. Yours is substanially larger than my bit though. PVA will just go brown I bet. A very nice looking set that Pilot, good luck with it. Andrew P.S. from the Bostik UK site re: Asbestos encapsulation: 'The 30-17 PVA sealer will permeate the materials and seal in any random fibres. Our protective sealer coatings can then be applied by brush or airless spray, resulting in a dried film that is flexible, durable and resistant to fire, water, mould and insect attack.' Doesn't mention heat from droppers in 70 year old radios though oddly. __________________ Invisible airwaves crackle with life. Or they should do. BVWS Member

24th Sep 2018, 9:31 pm	#4
turretslug Dekatron Join Date: Nov 2011 Location: Surrey, UK. Posts: 4,396	Re: Advice on asbestos in a 1930's radio. I'm in no way any sort of expert on asbestos handling, but I would be inclined to gently but thoroughly water-mist the asbestos part (using a trivial-cost horticultural-use spray bottle from a DIY shed, and having shielded the wood/electronics with polythene sheet) before applying the PVA- this will reduce the amount of dust when handling and brushing PVA, and will help the PVA penetrate and bind. If anyone has better/more informed advice, it would be good to hear but I fear that consulted expert authority might go a bit doctrinaire on "proper disposal" and so on. I'd also take it for granted that if the stuff shows up on finger touch, then the chassis ought to be cleaned outside with care over keeping the face away from the dust.

24th Sep 2018, 9:47 pm	#5
Radio_Dave Nonode Join Date: Jun 2004 Location: Norwich, Norfolk, UK. Posts: 2,543	Re: Advice on asbestos in a 1930's radio. I wouldn't paint anything on asbestos that wasn't specially designed for that purpose. If something you paint on it shrinks or peels off it's going to free fibres as it does so. Regards David __________________ http://www.youtube.com/ My Nixie Clocks

24th Sep 2018, 9:51 pm	#6
Phil G4SPZ Dekatron Join Date: Apr 2005 Location: Bewdley, Worcestershire, UK. Posts: 4,748	Re: Advice on asbestos in a 1930's radio. I understand that PVA can be diluted in water and then applied using a sprayer. Once dry, perhaps a heat-resisting automotive paint designed for exhausts etc could be applied. It does seem to be a huge sheet of material, when the heat rising from the dropper would be concentrated in one small spot, as evidenced by the dark mark above the resistor. I wonder if the sheet is original? An odd bit of design, too; you'd think placing the dropper lower down in the cabinet would have enabled a metal heat shield to be used, to duct the heat safely away from the cabinet top and out of the ventilation slots in the back, as in some round Ekcos. __________________ Phil Optimist [n]: One who is not in possession of the full facts Last edited by Phil G4SPZ; 24th Sep 2018 at 9:54 pm. Reason: Update

25th Sep 2018, 10:20 am	#8
MurphyNut Heptode Join Date: Apr 2016 Location: Croxley Green, Hertfordshire, UK. Posts: 979	Re: Advice on asbestos in a 1930's radio. Many thanks for the responses, Looks like sealing it with PVA and perhaps a coat of white heat resistant paint on top of that. I'll certainly feel happier having the Asbestos stabilized before spending time on the cabinet. Yes Andrew, it's a nice looking set and will I'm sure respond to a bit of TLC. __________________ Clive

25th Sep 2018, 1:38 pm	#9
dave walsh Dekatron Join Date: Jan 2006 Location: Ramsbottom (Nr Bury) Lancs or Bexhill (Nr Hastings) Sussex. Posts: 5,817	Re: Advice on asbestos in a 1930's radio. You'll have to seal it with something Clive whatever you decide to do. It doesn't look very original to me so I'd be inclined to seal and remove. A scrap of Aluminium as a heat shield would probaly be more in period anyway. There may also be an alternative low temperature voltage drop solution that could be employed while leaving the original dropper in place perhaps. Have you created any more of your amusing 1930's style video demonstrating the collection? Dave

25th Sep 2018, 2:37 pm	#12
Nickthedentist Dekatron Join Date: Jan 2005 Location: Oxford, UK. Posts: 17,846	Re: Advice on asbestos in a 1930's radio. I agree. I'm not too concerned about asbestos in radios, but that is a bit special! I'd remove it, and replace with something else and possibly do what Dave says and get rid of the dropper somehow. I would certainly be willing to sacrifice any authenticity in this instance. Nick.

25th Sep 2018, 4:42 pm	#13
dseymo1 Retired Dormant Member Join Date: Dec 2007 Location: Shropshire, UK. Posts: 3,051	Re: Advice on asbestos in a 1930's radio. I don't think PVA would be suitable for treating the asbestos should you decide to keep it in situ. PVA can be applied to sheet material, allowed to cure, then re-activated in the manner of a hot-melt adhesive using a smoothing iron. Clearly, that sort of re-activation is not desirable here.

25th Sep 2018, 5:22 pm	#14
kalee20 Dekatron Join Date: Feb 2007 Location: Lynton, N. Devon, UK. Posts: 7,082	Re: Advice on asbestos in a 1930's radio. It does look rather horrid design! Asbestos is an ideal material here - heat resistant, good thermal insulator. It will neither conduct heat to the wood of the cabinet, nor degrade itself at its hot spot. Thick aluminium as a shield will of course conduct heat from one side to the other rather well - but it'll also spread the heat out. So, you will have a warm-all-over cabinet top, rather than one which is hot at one particular spot. I share the misgivings of others about use of diluted PVA to an extent - it will degrade with the heat. But, I tend to think that the heat will be concentrated in one spot mainly, which is towards the middle of the sheet. So if you spray or soak the whole thing with PVA, the friable edges will stay intact, and the hot-spot (which looks as though it would stay relatively intact), if it loses its PVA there, will matter rather less. Personally I would re-site the dropper, mount it lower down, and horizontal. After all, that's what the Pilot designers probably had in mind all the time, they were just cut short and the radio rushed into Production before it was quite ready!

25th Sep 2018, 11:14 pm	#15
julie_m Dekatron Join Date: May 2008 Location: Derby, UK. Posts: 7,735	Re: Advice on asbestos in a 1930's radio. Forum member Ed Dinning has made autotransformers for the Bush DAC90, that reduce heat output considerably. Could you fit something like that in your Pilot? __________________ If I have seen further than others, it is because I was standing on a pile of failed experiments.

25th Sep 2018, 11:29 pm	#16
Yarraman Tetrode Join Date: May 2007 Location: Auckland, New Zealand Posts: 85	Re: Advice on asbestos in a 1930's radio. How about spraying the Asbestos with "VHT Paint" the type car mechanics use to spray manifolds ?

26th Sep 2018, 8:26 am	#17
Radiocruncher Hexode Join Date: Dec 2013 Location: Torrington, Devon UK. Posts: 446	Re: Advice on asbestos in a 1930's radio. Have a look at this thread that went pretty deep into the subject https://www.vintage-radio.net/forum/...d.php?t=144002 Regards Graham

26th Sep 2018, 8:46 am	#18
chriswood1900 Octode Join Date: Jan 2007 Location: Dorridge, West Midlands, UK. Posts: 1,483	Re: Advice on asbestos in a 1930's radio. When faced with a similair problem I safely disposed of the asbestos and used Superlux which has a very similair apperance see this site for details:- https://www.fireboards.co.uk/?gclid=...SAAEgJB0_D_BwE You should be able to get it from a local builders merchant. Chris