Historical Culinary Reconstruction "Excellent Quince Jelly"

I bought with my children the Quinces about 3 weeks ago and let them ripe in our kitchen closet because they were not yet "very ripe & yellow". The became more yellow and some started to rot so we decided it's time to use them.
We chopped them into a little thinner slices because my student told me that the jelly would be better if they are cut smaller and there is more surface contact.
We removed the seeds which felt very sticky, leaving a jellylike substance on our fingers. Some seeds had turned black and seemed to rot, in those cases we also trimmed the inner fruit a little.
While chopping we put the fresh slices into a big and a smaller pan. When Noor was done chopping, we put it on the stove on high heat.
5.10pm pan with cold water and quince slices on stove on 9
5.17 lightly boiling, the color of the peels turns darker yellow/orange
5.22 boils more vigorously
5;27 turned down to 6
5:37 it boils nicely and white foam particles started to form on the sides
It starts to smell nicely, fruity, full aroma,
5:47 turned it down to about 8 and let it boil for about 2 hours, refilling a bit
Of water to the small pan when the fruits were not anymore fully covered
And to the big pan. We did not measure how much we added, but I
Guess it was not anymore than about a 1-2 cups.
We started playing Monopoly, in between occasionally checking and stirring. To finis the game we left it I think half an hour longer than necessary to cook.
8pm ish we strained the decoction and fruits through a cotton kitchen towel, our mixture yielded just a little bit more than 1 liter.
Though the recipe advised to use about 1 cup of "Madeira sugar" for 1 liter decoction, we decided to start out with the half a cup of white refined sugar and to ignore the Madeira indication as our students mentioned it was way too sweet when following using the full amount mentioned in the recipe. Pim stirred vigorously and 1 cup white sugar dissolved quickly. Noor and Pim tried our decoction and really liked it. According to Noor and Pim it tasted really good, waving their hand next to their ear (Dutch gesture for delicious taste). It tastes like lemon, but then also sweet and a bit more like it smells, a bit more fruity(?) (too bad I was too rushed with preps next step to carefully listen to Noors description, next time definitely take all time to watch and describe).
We let it cook on medium heat and reduce.
10pm in the pan it actually does now look like a translucent deep red ruby color!!
And it smells heavenly and more and more seems to come close to Nostredamus description: "a jelly of exceptional beauty, goodness and flavour".
10 pm I did the jelly drop test, but it spread out on a plate. It tastes really good
10:23pm another jelly test "if you see when its cold that the drop holds quite round withouth spreading it is ready". Well its already much less spreading than before! And I think we find this good enough, want otherwise we will have reduced it so much that hardly anything is left. Lets wait 5 more minutes.
10:35 Well, the jelly test seems to remain almost the same, but I will pourt it now in a sterilzed glass container as I don't want to reduce it too much, and it's also delicious e.g. in yoghurt as a syrup.
10:37 I poured it into my (only) glass container of about 200 ml and it was still too much! So I poured it back into the pan and let it reduce for about another 100 ml.
11pm Oh no, got distracted and indeed me decoctions scorched at the side of my pan "which would give a bad color to my jelly". I try to pour it out immediately on the not-scorched side, hoping that the scorching would not really effect the remaining jelly on the bottom, which still seemed to look fine, but perhaps it lost some of its transparency? I filled it into the glass container and it looked very dark red, but then surprise! When I put the glass container in front of my iphone light, it glowed in a wonderfully ruby red color!! See below
I wonder whether the glass has an impact on the color effect, because the color appears much more brownish in a plastic container (see below). But still it's amazing if you put the very first images of the dryish, pale yellow quince slices next to the final photo of the ruby red quince jellylike decoction -what a great color change, adding onlywhite sugar and without adding any colorant!