 So, I have this old printer. I'm actually going to discuss it in a future video. Today I just want to talk about the case, which has problems. On the back, there's this manky adhesive residue which I can't get off, but the biggest issue is the way the plastic has all gone yellow. This is because it's been left out in the sun and ultraviolet light has attacked it. Anywhere that light could reach has gone brown. The inside and bottom are still relatively white, but anywhere where there was a label becomes really obvious. Luckily there's a fix for this, retrobriting, and I've been wanting to try this for a while. The chemistry behind the yellowing plastic is complicated, but it's mostly due to ultraviolet light attacking the bromine-based fire retardant in the plastic, which causes them to degrade and turn brown. Retrobriting hides this using the bleaching effect of hydrogen peroxide. The best technique varies depending on who you ask. Some people swear by Salon developer cream and ultraviolet light, as it's cheap and works well, but right now I'm in Scotland in the middle of winter and UV is hard to find. What I'm going to try is hydrogen peroxide solution and heat, which I've seen give good results. To make the hydrogen peroxide I'm actually going to use sodium carbenate powder, which generates hydrogen peroxide when dissolved in water and is a lot easier to handle. Some people use household cleaner for this, but I've got some of the pure stuff. The first stage is, of course, to dismantle the device, as I don't want to clean any of the electrical components. They probably wouldn't like it. The printer comes apart relatively easily into a pile of plastic pieces. The next stage is to weigh out the sodium carbenate. I did try to calculate how much I needed, but the maths didn't produce a sensible answer, so I just ended up with some. About 80 grams. Next, this will assemble the reaction vessel. I don't have anything temperature controlled, so instead I'm just using lots of hot water tank insulation to stop it getting cold. It's great stuff. The biscuit tin is, of course, Jacob's crackers. We now place all the components into the box, carefully packing them and add water. This is at about 60 degrees centigrade. I didn't want to go much hotter than that in case the plastic deformed. The printer is not particularly well made. I also add some genuine Scottish rocks to hold the plastic down as it tends to float. Once done, I'm ready to add the sodium carbenate after donning the appropriate protective gear. In the hot water it starts working immediately, releasing oxygen. I then cover it to prevent heat loss, and now there's nothing to do but wait. After a couple of hours I open it up again to check the temperature. It's dropped to 53 degrees, so I add some more hot water. This will dilute the solution a little, but I think it's more important to be hot than strong. Finally, after four hours I decide it's finished and remove the pieces. The water is scummy and horrible, but the plastic doesn't seem to have changed much. Luckily, it does all go back together again, which means the plastic hasn't warped. Unfortunately, the amount of yellowing hasn't changed, so the process hasn't had any effect there. It is, however, much cleaner. All the adhesive gunk has come off, and the ingrained dirt in all the scratches has come off too. That part was certainly a success, not one that I expected, and well worth doing. I do have a few theories as to what went wrong. The commercial cleaners contain a catalyst, tetraacetyl ethylene diamine, or TAD for short, which my pure compound didn't have. That might be necessary. My solution might not have been strong enough, or maybe I should just have left it in for longer. I do want to be careful what I do, though. Retrobriting does damage the plastic. If anyone has any other suggestions, do let me know in the comments. I would like to try this again, but in the meantime, I think I will enjoy my nice clean printer.