I've started hardening off my Peppers & Tomatoes to get them ready to stay outside. They're getting to be too large to keep under my light indoors and I really want to start some Herbs when these stop taking up space. When they're ready to remain outside they're going into some really large 18" pots.
I didn't do this last year so I'm really not sure if I'm doing it right, but we'll see how it turns out in a couple of weeks. For the past couple of days I've put them outside when I get home from work (about 5 PM). I leave them outside until dark and bring them back in. That's about 45 minutes. I've also reduced their watering, but today (two days later) I've had to water them to keep them from wilting. The main problem is the biodegradable pots that tend to dry out very quick. Today (Saturday) and tomorrow I plan on increasing their time outside to about two hours. Next week I'm probably going to leave them outside from morning to noon. Hopefully by mid-next week they can just stay outside 24/7.
TIP: Carrying plants outside two at a time is sort of exhausting; though my dog Squish loves the activity. To make it easier I've put most of the plants on low profile produce crates and trays.
Why do I do this? These plants have spent their entire lives, so far, indoors under artificial light in a controlled environment and have never seen real sunlight. Artificial light is no comparison to the real sun. Just like you, these plants will burn up if not acclimated first. There is also wind, changes in temperature, and more frequent drying of the soil. These plants will not do well unless acclimated to these conditions first; otherwise they might very well die.
The picture on the right shows what happens to your plants if you leave them out in the weather and sun without hardening. This tomato was one of many that I didn't have room for under the light indoors. This plant is also somewhat shaded on my patio. Since I just can't get myself to trash them I've cut them back to see if they'll survive. They're the same age as my other tomatoes, but they're a third of the size.