Leslie wrote:

I left the aluminium bare as it is. Tried to spray it with clear coating but that became messy and looked unnatural.

The problem is, if you leave the aluminum bare it will not continue to look good...you'll need to 'harden' the surface (as B&O does).
Well -you can not do it as they do in the factory 😕 But -the solution for amateurs is...sodium hydroxide.

I once bought a set of badly damaged alu C 30's with lots of scratches. I sanded the surfaces and afterwards i gave it some "Caustic Soda" dissolved in water (Sodium hydroxide) to harden the surface. It looks very close to the original finish. I think it's better than some clear lacquer.

Steffen wrote:

Leslie wrote:

I left the aluminium bare as it is. Tried to spray it with clear coating but that became messy and looked unnatural.

 

The problem is, if you leave the aluminum bare it will not continue to look good...you'll need to 'harden' the surface (as B&O does).
Well -you can not do it as they do in the factory 😕 But -the solution for amateurs is...sodium hydroxide.

I once bought a set of badly damaged alu C 30's with lots of scratches. I sanded the surfaces and afterwards i gave it some "Caustic Soda" dissolved in water (Sodium hydroxide) to harden the surface. It looks very close to the original finish. I think it's better than some clear lacquer.

Thanks Steffen for the tip. I have made some alum. base (feet) for my Beovox replica's and polished them about 3 months ago and they still look great. Also for my Grundig tweeters which you can see on the background. They look fantastic...

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Steffen wrote:

But -the solution for amateurs is...sodium hydroxide.

Steffen, does the polished aluminium stays bling bling when I use this caustic soda stuff. What's your exeperience? Never knew you have this soda in almost each household.

Leslie wrote:

Steffen wrote:

But -the solution for amateurs is...sodium hydroxide.

Steffen, does the polished aluminium stays bling bling when I use this caustic soda stuff. What's your exeperience? Never knew you have this soda in almost each household.

And how do you mix it ?

Søren Mexico wrote:

Leslie wrote:

Steffen wrote:

But -the solution for amateurs is...sodium hydroxide.

Steffen, does the polished aluminium stays bling bling when I use this caustic soda stuff. What's your exeperience? Never knew you have this soda in almost each household.

And how do you mix it ?

 

And how long does it has to stay in? Seen some videos on

My experience is, that "raw" aluminum is very sensitive to fingerprints etc.

When you use sodium-hydroxide it will not stay bling-bling (if you by this mean "shiny"). The surface becomes a little more "white" - like the brushed aluminum surfaces on the "old" B&O -like the Beocenter 9000 and BeoSystem 5500 etc.
When I sanded my speakers they became more shiny than the original finish - after the sodium-hydroxide they look more like the original.

I once made a new alu-plate for the dust-cover of a Beogram 5500. I bought a thin alu-plate, sanded it and put it in a sodium-hydroxide solution for just a few minutes.
Actually - I don't have an excact recipe...I just pour some water in a tub and then I put some caustic soda in, and then it must be stirred (not shaken) 😕 - till it's dissolved.

In case of the speakers, I dipped a cloth in the solution and gently rubbed the surface for a few minutes, untill it looked right.
BE CAREFULL - use rubber gloves and eye protection! 
Finally you rinse with water and wipe the surface with a piece of dry cloth. Voila!

I've seen some of the videos on YouTube - Don't try this at home, kids 😂

When anodizing aluminum, the only time you use caustic soda is when you have old pieces already anodized, you use the caustic soda to strip the surface down to raw alu, thereafter you anodize. What you get after inmersing in caustic soda is raw alu which wil oxidize, starting immediatly with contact to air, the oxide will give a "whiter" look and the oxide will also, to some grade, seal the surface, but any liquid like coke or beer will penetrate the surface and accelerate the oxidation and give a "whiter" area, and after years the aluminum, like iron, will disappear and all what's left is the oxide. The surface can be protected to some grade with wachs, Pledge or some oil, but it will continue oxiding.

Anodizing closes all pores in the material and hardens the surface, making it withstand all not acid liquids and to some grade scratch resistant.

Sorry Steffen, when I read your reply, it triggered something I learned long time ago and I had to do some homework.

What B&O do with aluminum is something amazing and is known throughout the world as one of the best, they are now experimenting with a way to make a totally white (without dyes) aluminum   

Thank you both for explaining, very interesting to read. With "bling bling" I mean shiny, that's right! I think I leave it that way and I don't mind the finger prints as long as I can wipe it off. It's like an Iphone🙂

Leslie wrote:

Thank you both for explaining, very interesting to read. With "bling bling" I mean shiny, that's right! I think I leave it that way and I don't mind the finger prints as long as I can wipe it off. It's like an Iphone🙂

I have made good results with marine grade poly urethane varnish, it more stable in color (cheap ones gets yellow), but you dont find it in spray cans, so you will have to use a spray gun, just before spaying, a light polish and wipe of with acetone, spray 2-3 layers, polish before each layer, use cotton gloves to handle.