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This is the image with the LEDs at the top and the vertical stripes are the reflections.
Second attempt to post an image, this time with a smaller file size.
Thank you ! Your article inspired me to make a long-needed ceiling light over a kitchen worktop. I stuck 5 LED strips, each 2 meters long, and connected them in parallel to a 12v 10A DC laptop power supply. Because I did not want the light to glare over the dining table, I mounted the strips on an L-section extruded aluminium strip, so that the LED strip was mounted parallel to the ceiling and the vertical part of the L acted as a shade/ reflector. Unexpectedly, the aluminium's fine marks along the direction of extrusion diffract the LED light, creating a very pleasing appearance of 3D in the reflections, which I have tried to show in the photo attached.
This is a great demonstration. Presumably you have to start with a low-carbon mild steel, or the rods will not bend easily. You could extend the demo by smearing the central part of the rod with case-hardening compound to introduce extra carbon before heating, then clean up and check the strength and hardening before and after annealing. As jtobako says, the interference colours are also instructive: yellow is a good tempering colour, blue is a nice decorative one which apparently gives a little corrosion protection. With such a thin rod the interference colours may run along very quickly, so heat carefully when tempering!
LEDs and Lighting Class
Welding Tools and Materials
Welcome to Welding
Scotchbrite General Purpose scouring pads, such as are sold in hardware stores, contain mineral particles ( probably aluminium oxide, which is the same as emery). They are capable of scratching both steel and glass. If you want to avoid this you have to find grades specially made for cleaning non-stick pans.
This is very helpful. I have been looking for a suitable circuit on Google but did not find this simple use of a 555 IC. Thank you!