Why must halogen lamps always be used with a piece of glass in front of them? Because they are hot to the touch running hotter than ordinary incandescent bulbs?
Yes, but the heat causes other, less obvious, even invisible issues that you need to be aware of. Issues that the glass protects you against.
In this video, I take a closer look at them.

https://spectrum.ieee.org/energy/environment/our-best-lamps-still-cant-equal-the-luminosity-of-the-sun

Matt’s out and about on site talking about the benefits of fitting LED lamp over halogen GU10’s. Matt carries out a bit of basic mathematics to prove the energy efficiency saving when using LED lamps.

In this video I tested a Chinese LED strip rated for mains voltage. It runs directly on 220 / 230 / 240V AC with no power supply. The listing says it’s waterproof. This definitely raises some questions. I couldn’t resist the temptation to test how waterproof it really is.

Today I take a look inside a party disco light. It’s simply an RGB LED lamp with a rotating disco globe (dome) on top of it. It projects moving red, green and blue beams. It has an E27 (E14) screw base, so you can install it into any ceiling light or table lamp. It runs on 230V 50Hz mains and draws about 3W. I reverse engineered the full schematic of it. The power supply was a bit different than I expected :).

This is a teardown of a Chinese insect zapper (or mosquito killer). It has a completely mad circuit that makes no sense – probably a totally botched up conversion from a fluorescent tube to a UV LED).

Testing a mains voltage LED from China. This one is rated 220V and 20W. It really can be connected directly to AC mains with no LED driver. 30W and 50W versions are also available. In the listings it’s called “smart IC” or “integrated driver” or “driverless” COB LED.

“Mains to breadboard interface.” ;)
dat SOMY branded TV

Today I took a look at a very dangerous LED lamp from China. The board with the 2835 SMD LEDs has no cover and the LEDs are live at mains voltage. Live terminals exposed! It also has no fuse, poor heat sinking, no inrush resistor and the actual power is not what the listing claims.

Opening and examining a 3W LED reflector light bulb made by Livarno Lux. It cost me an equivalent of $1.75 in Lidl supermarket.

Why are LEDs so much more efficient than incandescent light bulbs? Do LEDs have disadvantages?