You could use a sous vide (immersion cooker) rather than a heatlamp. The liquid 40-volume peroxide is better than the gel type. Don't paint it on, just mix it in the water. As far as the UV, it may be more the heat than the UV that speeds along the retrobriting.
8-Bit Guy and Retro Man Cave have a few videos on it, including doing it indoors.

Smack2k wrote:

Can you use liquid peroxide in the container with it? Odes that pour in on top of the foil?

The8bit Guy have done it with liquid peroxide. Just remember to have the stuff submerged all the time.

IME heat works at least as well as UV.

A few new ozone generators under $40 have been popping up in the market recently, it may soon be possible to do this with a heat lamp, box and ozone generator. Well-ventilated areas and/or well-sealed boxes only.

Thanks, will check out their videos....want to make a box for it as winter is here and I have several things I'd like to retrobrite....

EDIT - Does anyone happen to know if sous vide sticks are only good for smaller pots or do they work in larger ones to? I have some case fronts (Couple Macs and a VIC-20) that I am going to retrobrite. Not much direct sunlight right now or till March in my area, mostly overcast and chilly / cold so indoors is only option. Sous Vide stcks look nice, but arent cheap from what I see, so wondering if they work in larger tubs that would hold the front of a Mac PowerPC Desktop front?

Merovign wrote:

IME heat works at least as well as UV.

A few new ozone generators under $40 have been popping up in the market recently, it may soon be possible to do this with a heat lamp, box and ozone generator. Well-ventilated areas and/or well-sealed boxes only.

Ozone give a slight, yet not effective enough result. As you said, heat is better, wayyyyy better. UV and heat are the way to go. Some have even suggested that you finish it up, with the use of some sort of oxygene/UV filter spray, yet if used, it is better for plastic that you do not touch. As I think it will leave a coat, that makes the feel of the plastic quite wrong when you touch it. And yeah.... How longer will these things survive, before being unrepairable? 20 years from now? 30? 40?. Nothing lasts forever.

brostenen wrote:

Nothing lasts forever.

Also plastic is biodegradable...it is only matter of time. 😀

When you are using retrobright you will only remove external layer of the yellowish thing, but soon the internal thing starts to emerge and the process also accelerates yellowing.
The only way to keep plastic white is applying retrobright about every 4-6 months.
You can do it on april, as the day becomes longer, and on september.
I think if you do it a lot of time you can extend the period up to a year (or two but I did not tried).

If you have patience, you don't need any additional equipment. I'm doing all retro-brightin indoors, at any time of the year. It just takes longer. I usually use washing bleach and let it rest in a closed clear plastic box for a week. Works fine.

brostenen wrote:

As I think it will leave a coat, that makes the feel of the plastic quite wrong when you touch it. And yeah.... How longer will these things survive, before being unrepairable? 20 years from now? 30? 40?. Nothing lasts forever.

This. I do worry that brightening attempts will make these plastics brittle. They're pretty cheap to start with.

Plastics in general have been holding up pretty good indoors. I've got toys going back into the 60s, and I've been really impressed how little of it shows any degradation. Even slot cars that have been nasty with petroleum oil. Just the rubber tires go dry. And sometimes even those are fine. (The tires actually can be 'restored' a little with oil. Go figure.)

We've had brightening attempts nearly as long as we've had a web -- surely some of us have some early experiments. How are these now?

Ditto those car-upholstery dye jobs. (It's okay. You can claim a "friend" did those.)

derSammler wrote:

If you have patience, you don't need any additional equipment.

I couldn't agree more. People just want to rush things and add unnecessary catalysts.
The key is to do it slow.

1. No catalysts of any kind! This includes laundry boosters and bleach.
2. Room temperature only! Warming (or heating) the peroxide bath speeds things up but also causes too much oxygen release at once that damages the plastic. Heat it too much and the plastic will melt.
3. It's pointless to use too strong peroxyde solution. 15% is more than enough.
4. Peroxyde decomposition is a very slow proccess so a peroxide bath can be reused many times as long as it's clean.
5. Using an UV lamp or exposing the peroxide bath to direct sunlight is unnecessary. Placing the container next to the window is more than enough.
6. Cover the container but don't make it airtight. Allow the excess oxygen to escape.
7. Use rubber gloves at all times. If you get peroxide on a wound you will understand what real pain is.
8. Patience! Good results take time.
+1: Some plastics won't brighten at all no matter what.

You don't have to worry about the plastic getting brittle after 20 years. I rearticulate animal bones as a hobby and it is the same proccess. This cat was my first project 15 years ago and it's in very good shape, no change in the bone structure at all. Beautiful as ever.

I brightened a piece of 5.25 bay cover today to demonstrate the effectiveness of this method.
It was placed in a 15% cold H2O2 solution and put in the window, not exposed to direct sunlight at all. It took exactly 12 hours to achieve this level of brightness (compared to the other cover I didn't brighten). You can do it in the basement if you like, it just takes longer.

Miphee wrote:

You don't have to worry about the plastic getting brittle after 20 years.

I think it is more debateable, if we look at what plastic we are talking about and how it have been handeled. Plastic do get brittle over the years. It is just a fact of matter decomposing over time. Another factor is how it was handeled. If you have had it sitting for 20 years, then it is much stronger than plastic that have been handeled. Temperature change is another factor that impacts the material. You just never know what the material have faced over 20 years of use and non use. ABS is more sturdy than Nylon or PVC for that matter. Like my girlfriend's music keyboard stand have been sitting for 10 years in a garage, and the first time we had to tighten then lock to have it sat up again, the nylon-knob just cracked and splitted.

But yeah.... Depends on the material and what action it have seen over the years.