Author Topic: UK GPO 746 Topaz Yellow Telephone Restoration  (Read 4616 times)

Offline royalbox

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UK GPO 746 Topaz Yellow Telephone Restoration
« on: January 16, 2017, 09:01:58 AM »
I thought I'd document my attempted restoration of this UK GPO 746 telephone I recently bought and hopefully get some tips along the way. It's from 1971 and is in the less often seen "Topaz Yellow" which is a mustardy yellow, but is badly discoloured. I've already made a start, but first here's some pictures of the phone taken by the seller.

Barry.

Offline royalbox

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Re: UK GPO 746 Topaz Yellow Telephone Restoration
« Reply #1 on: January 16, 2017, 09:11:11 AM »
Here's after cleaning showing the original colour under the dial surround.

Offline royalbox

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Re: UK GPO 746 Topaz Yellow Telephone Restoration
« Reply #2 on: January 16, 2017, 09:22:56 AM »
Here's after sanding with 600, 1000, 1500 grit wet and dry. I've only done the initial 600 grit on the handset in this picture. I'm waiting for some 2000 grit to arrive as well as they didn't have any locally.

As you can see, I sanded half the handset at a time as I wanted to prevent flattening the divider line running down the centre as much as possible.

Barry.
« Last Edit: January 16, 2017, 09:30:28 AM by royalbox »

Offline royalbox

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Re: UK GPO 746 Topaz Yellow Telephone Restoration
« Reply #3 on: January 16, 2017, 09:41:40 AM »
Now, here's a question: Has anyone here tried "acetone vapour smoothing" as used by people doing 3D printing with ABS? I found a post asking about it but haven't found a post where someone has tried it. It seems it could be a good way to smooth out the final sanding scratches if done carefully.

Barry.

Offline twocvbloke

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Re: UK GPO 746 Topaz Yellow Telephone Restoration
« Reply #4 on: January 16, 2017, 11:09:20 AM »
Not acetone, but Methyl Ethyl Ketone (or MEK) has been used for smoothing the plastics of restored phones:

http://www.classicrotaryphones.com/forum/index.php?topic=5260.0

Offline royalbox

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Re: UK GPO 746 Topaz Yellow Telephone Restoration
« Reply #5 on: January 16, 2017, 04:21:08 PM »
Yes, the vapour smothing post I found took me to that post. It would use a lot of liquid to dip even half the phone at a time I think. I want to try the vapour method but perhaps I'd need to wait for the warmer weather so I can do it outdoors for safety. Not sure. Would like to hear if anyone has tried it though.

Barry.

Offline andy1702

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Re: UK GPO 746 Topaz Yellow Telephone Restoration
« Reply #6 on: January 17, 2017, 08:18:55 AM »
From what I've seen of the vapour smoothing for 3d prints it seems to reduce the overall definition. In prints with the 'steps' in them it's desirable, but on a phone that may have embossed detail it might damage it. My guess is you'll end up with something that looks like rubbed hallmarks on over-polished silver.

I think the best way is a liquid retrobright bath. However the jury is out if that method is permanent or not.

Andy.
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Offline royalbox

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Re: UK GPO 746 Topaz Yellow Telephone Restoration
« Reply #7 on: January 17, 2017, 01:01:21 PM »
Hello Andy,
I've got rid of the discolouring with sanding, my aim is to try and smooth out the sanding marks as much as possible before polishing. I was thinking that a stuff time in the vapour may be enough to do it as the scratches will be very fine, especially when I do the final 2000 grit. Nothing like those ridges on the 3D prints you see on youtube.

I'll have another read of that dipping method thread but I'm not sure how easy or cheap it is to get those chemicals here in the UK.

By the way, have you seen this ebay seller selling brand new 746 cases? I wonder if he got hold of an original mould. Not buying one just thought it was interesting.

Barry.

Offline andy1702

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Re: UK GPO 746 Topaz Yellow Telephone Restoration
« Reply #8 on: January 17, 2017, 01:38:39 PM »
Hi Barry,

That MEK stuff is commonly sold by model shops here in the uk in a little glass bottle under the name of 'Plastic Weld'. It's used for assembling plastic scale models without the mess of glue that goes all stringy. I think I'd be tempted to try a very fine mist spray of acetone personally.  You need to absolutely soak the surface so the plastic liquifies and then sets again nice and flat. I think you'll have problems on vertical surfaces because the thin layer you melt will want to run down and you'll get an effect like the really old glass in church windows where it's thicker at the bottom than it is at the top.

Regarding that E-Bay seller, I bought some new clear dial opelsfrom them. They're pretty good and I'm getting ready for some more. However you have to be careful because some of the things they are selling are to their own design and not at all historically accurate for the purposes of restoration. The dial finger wheels are wrong, because proper coloured finger wheels have a brass and steel spring embedded into them which you put a screwdriver under to flick the dial opel out. Also orange 746 cases never existed in reality. A very small batch were made as a test, but they never went into production. Also the alpha numeric dial plates for fitting to dial 21 were only ever made with a white background (these guys do a cream one) and were only fitted to dials with black finger wheels, which were a replacement for dial 12s on bakelite phones. As far as I know they were never used on 700 series.

Also the alpha numeric dial bezels in various colours are not correct. they should be flat (without the lugs to hold them in place) and made from a clear plastic, with the lettering and background colour applied to the back then secured to the phone using a metal ring fitted to the inside. The GPO would never have allowed a plastic ring with the printing on the surface because they knew the printing would rub off with many years of heavy use.

The buttin blanks are quite good, but the coloured buttons for 746 tyes themselves never existed. Like the finger wheel they were always clear on a 746 to cut down on the stock keeping requirements of different types. You can have coloured ones for a 706 though.

Of course accuracy doesn't matter to some people, but personally I always try to restore things the way they were, not 'enhance' or change them. I guess that's my museums background showing through!  ;D

Andy.
Call me on C*net 0246 81 290 from the UK
or (+44) 246 81 290 from the rest of the world.

For telephone videos search Andys Shed on Youtube.

Offline royalbox

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Re: UK GPO 746 Topaz Yellow Telephone Restoration
« Reply #9 on: January 17, 2017, 03:36:20 PM »
Thanks Andy for the tips. Interesting information about that reproduced stuff on ebay. I knew that the coloured buttons were not provided originally but didn't know about all the other things you mentioned. Also I think a new case with an old handset might look a bit odd. I expect the colours and finish wouldn't match quite right.

Anyway, as I say, I wasn't going to buy one. The enjoyment is in trying to restore the old ones for me, even if I'm no expert.

Barry.

Offline royalbox

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Re: UK GPO 746 Topaz Yellow Telephone Restoration
« Reply #10 on: January 18, 2017, 04:13:37 PM »
The 2000 grit wet and dry sandpaper arrived today, won't be able to do any sanding until the weekend now.

Offline andy1702

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Re: UK GPO 746 Topaz Yellow Telephone Restoration
« Reply #11 on: January 19, 2017, 11:24:54 AM »
I've only tried sanding one phone as an experiment. It's an ivory 706 that had discoloured to a very dark yellow. I found it really hard work and discovered I needed quite coarse sandpaper to get the discolouring off. Then I finished with finer grades wet with T-Cut. To finish I used wire wool, again with T-Cut. Final polish was yet more T-cut on a rag.

Another thing I tried was a dremmel type thing with a polishing mop. Don't even bother trying this... It spins too fast and creates too much heat, which starts to melt the plastic and take little gouges out.
Call me on C*net 0246 81 290 from the UK
or (+44) 246 81 290 from the rest of the world.

For telephone videos search Andys Shed on Youtube.

Offline twocvbloke

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Re: UK GPO 746 Topaz Yellow Telephone Restoration
« Reply #12 on: January 19, 2017, 01:11:04 PM »
Yeah, if using a machine polishing tool, you need to slow it right down for plastic, higher speeds are more suited to metal, though even brass can break apart if it gets too hot when polishing (as I know, ruined a cheap duplex burner lamp about 10 years ago polishing it with a Kirby Handy Butler polisher, which was just way too fast and harsh for the brass)...

Offline royalbox

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Re: UK GPO 746 Topaz Yellow Telephone Restoration
« Reply #13 on: January 20, 2017, 10:05:18 AM »
Thanks for the tips, I won't use any type of drill on it.

I've just re-read the thread twocvbloke linked to earlier. It ends without any definite conclusion, no final results of a whole phone. Still, I think it might be interesting to try this dipping method.

You can get MEK quite easily on ebay it seems but he suggests mixing it with thinners. As the scratches on the phone are quite fine (I've done up to 2000 grit now), I wondered if a weaker mix of MEK with thinners would work. Not sure whether there is any benefits with using acetone vs MEK.

As I just bought a badly discoloured two-tone grey 746 for little money, I'm going to sand the main case on that and experiment on it first. I'll update as I go along in case anyone's interested.

Barry.

Offline TelePlay

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Re: UK GPO 746 Topaz Yellow Telephone Restoration
« Reply #14 on: January 20, 2017, 10:31:05 AM »
There are quite a few topics dealing with chemical smoothing by dipping, vapor and most recently, chemical sanding. This is but one but one which I've found to work quite well.

     http://www.classicrotaryphones.com/forum/index.php?topic=17145.msg176752#msg176752

I've taken scratches out of ABS and soft plastic using a coarse sand paper (320, 400 or 600 with water depending on the depth of the scratch) and worked my way up to 1000. Then using a mixture of 50/50 acetone and denatured alcohol or straight denatured alcohol on a rag, have been able to get rid of the 1000 grit sand marks quickly. Got it to a point where Meguiar's, Novus 2 and/or buffing would produce a flawless finish.

I started with 10% acetone and worked up to 50%. More than that "cut" too much and left cotton cloth marks on the surface. It's a trial and error leaning curve for each person. Then intent of chemical sanding is to remove a thin layer of plastic just as sanding would but with a solvent and cloth, no additional "sand" marks are created.

You can search the forum for chemical sanding to find other topics. This is one from a few months ago where Christian used denatured alcohol on soft plastic to a remarkable end.

     http://www.classicrotaryphones.com/forum/index.php?topic=17163.0

You may want to give this a try. Minimum expense, effort, time and danger for maximum results.
« Last Edit: January 20, 2017, 10:33:06 AM by TelePlay »
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