A candle factory period, which started with 'Bougies 2000', a toy I had for Christmas and ended the next year at Christmas at our place with dozens of personalized candles of various shapes for each guest.
Various gadgets made of cardboard and yellow scotch tape - I got a stock of nice thick tape from my cousin's optic shop. I used so much cardboard that the bottom of every box of the house disappeared into my creations. One that I remember was an 'electric dice'. Six light bulbs were wired to an random rotator moved by an electric motor. You ran the motor during a period and when it stopped the remaining one was the choice of random. This gadget worked so well I brought it to school where it had a little success with my geek friends.
Today, with computers, you can get this with one line of code:
Print Random( 6 )
I also has a very intense 'photo-laboratory' period. No smart phones at the time, photos were done with chemical, and I got a black and white photo laboratory kit for one of my birthday. I immediately setup my personal laboratory in the top of the building in the a small cupboard. There was no water, and part of the fun was to install a sink made out of plastic basin and water supply with aquarium pipes. Unfortunately there was no lift in the building so I had to carry the water up to fill the tank, and also down to throw away the chemical waste.
The next gift was a real reflex camera to build yourself (an expensive gift from my parents who saw me so impassioned by photography), and soon I was the official photograph of the family.
I will always remember the red light of the laboratory and the excitation of seeing the picture magically appear when you put the paper in the developer. The chemical had a specific smell and soft touch to the finger. I kept this laboratory until I was 21, at the time with much better equipment in the house we had after the apartment.
Like many kids, I also had a 'chemical laboratory' period, based on 'Chimie 2000' another toy of the '2000' series chosen by my father. It ended abruptly by a fire in the kitchen that scared the hell of out me and my mother.
After the fire, my brother and I started to cultivate crystals. It is a fascinating and simple experience that I would love to do again today. By over-dissolving a chemical compound like copper-sulfate in hot water, and letting it rest for days, crystals start to appear. You then select a nice one, hang it on a wire and make it grow for month. You obtain magnificent crystals of pure blue for copper sulfate. Other color and shapes were also possible with other chemicals like potassium ferrycianide.
I was also interested by mechanics. We had the luck of having an old Solex motorcycle. Solex were small motorcycles very popular in France in the 60s. Their particularity was to have a small engine on the front wheel and not under the seat as usual. This construction made them very cheap to produce. Propulsion was ensured by a pebble under the engine pressing on the front tire, which was problematic under the rain. The engine was not very powerful and a Solex could hardly reach 30 km/h, but the engine was so simple and well thought that I must have dismantled it completely to remount it 10 times, discovering the principle of a two stroke engine. I was not old enough to drive it in the street (11!), but I could use it for promenade along the river in front of the apartment, and was so proud when the engine worked again after being torn apart and remounted!
Certain evenings, my father came back with work to finish. He usually brought back with him one of the first electronic calculators, a large device with a tube-display. My brother and I waited impatiently each time for having the authorization to play with it after his work was finished. We spent hours just doing calculations and playing with the machine to see the wonders of modern electronics.
But all these projects were nothing compared to the number of machines I created with the best toy of all, Fisher-Technics!