Retrobright ATARI 1040 STF – attempt no. 3
And here we are with another episode of the popular ATARI STF whitening series 🙂 After the previous failures with wrapping the parts in stretch film in Retrobright ATARI 1040 STF – attempt no. 2 and the earlier Retrobright ATARI 1040 STF – attempt no. 1, I decided to take the whole process to a more professional level. There are several different whitening methods, but all of them use some kind of peroxide solution. It is important to realise that different plastics behave differently: stretch film may work well for some people, while for others it can cause unpleasant and probably permanent stains, created when condensed moisture washes the peroxide away inside the enclosed film. I did not want to risk another failure because whitening always takes quite a lot of time. I also did not want to depend on the weather and have to expose the items to sunlight. I want to be able to whiten plastics in winter or in bad weather too.
I asked Marek Nýdrle whether he could provide me with four LED modules fitted with UV LEDs. He kindly helped me out and supplied the modules for my purposes, for which I would once again like to thank him very much. I thought about what kind of container to use for the whitening process and how to make an enclosure for it, because looking directly at UV light is not exactly pleasant. First I arranged for a local glazier to make a low glass tank from 5 mm tempered glass. I slightly regret not having a hole drilled in it so that I could fit a valve and drain liquid peroxide more easily.
For a long time I wondered what to make the enclosure from and how to build something into which I could install everything and start whitening. My wonderful wife came up with the idea of using a photo lightbox that I had bought from AliExpress about three years earlier for taking photographs against a white background. It was a brilliant idea because the photo box can be assembled quickly, is easy to handle and is simply ideal for the job. Its entire inner surface is covered with reflective silver foil, which further improves the distribution of UV radiation from different angles.
On Friday evening it was time for our Atari club meeting in Kevin’s Atari room, and it was obvious that we would want to test the whole whitening process. For the first attempt we used two UV LED modules and coated the item being whitened — my ATARI STF — with 12% peroxide gel. Exposure time was approximately two hours and 45 minutes. We temporarily attached the UV LED modules to the original LED modules intended for photography. They became quite hot and it was obvious that they needed cooling. We finished at about two in the morning. At first glance it looked as though the stains had disappeared. I took the Atari home and showered and dried it during the night. The stains caused by the previous whitening in stretch film had not disappeared. Overall, however, there was some visible improvement across the whole plastic surface. The result did not exactly amaze me, though.
On Saturday morning I bought three litres of 30% peroxide and rubber gloves at the local Jednota shop, determined that I would not sleep peacefully until my Atari was properly whitened. When buying the peroxide I had to provide my address and state the purpose of the purchase. Fine… but apparently it does not bother anyone that the caps leak. In the evening I drove to work and milled custom heatsinks on the CNC router for the UV LED modules. I was in a hurry, of course, and various obstacles got in my way — changing the milling cutter, measuring something incorrectly and so on… I really need to work more calmly. My impatience is my excuse. After 9 p.m. I was back with Kevin in the Atari room. This time we used all four UV LED modules and positioned them roughly 30 cm from the Atari. We again used the gel and at the same time tried whitening one extremely yellow key. The heatsinks worked brilliantly. I had not slept much after the previous night, so sometime after midnight I went home, leaving Kevin to keep everything running until morning and send me an update.
In the morning Kevin initially had good news, but after washing and drying, the stains once again became visible. The key, however, looked good — I would say about 80% satisfactory — with only a slight transition visible where the key had never yellowed. Without me, Kevin then tried whitening keys in 30% peroxide, leaving the setup running from 8:00 p.m. until 7:00 a.m.. The result was absolutely amazing, as you can see in the comparison photos. If only it would work on my cursed stains too. We do not yet know how many times the peroxide can be reused, but we are now going to start whitening at full speed so that we can gather as much experience as possible.
In the photo on the right you can see a comparison of the different whitening methods after 11 hours of exposure under the UV LED modules — from left to right: 30% liquid peroxide, 12% peroxide gel, untreated.
We streamed the whitening on YouTube and some of it on Facebook as well. Perhaps one day we will edit it down, or more likely prepare a completely new demonstration with more useful information and without the idle sections. So please excuse the dead spots in the video and the occasional embarrassing moment. We are looking for the ideal streaming setup and also trying to find out whether there will be any interest in it.