Marrow & ginger jam

I made this recipe today without jam sugar and without leaving it overnight. I still got a good set (even though I ran out of gas halfway through!), and is a good bit darker than the illustrative picture but it still tastes damn good even while hot. The steps I took to ensure a quicker set are: 1. Heat the sugar in an 80c oven for a good while to warm up before adding it to the fruit. 2. While I pre cooked the courgette, I poured some juice from the pan into a second pan to reduce it. 3. I heated the lemon juice and other ingredients in the second pot before adding it into the main pot containing the courgette and sugar. 3. I used a hard boil instead of a simmer for the jam-making stage (as hot as you can go without throwing jam all over the stovetop). 4. I tranferred some of the liquid jam to the same second pot to reduce faster. Looking back, it would have been much easier following the recipe, but with practice, you learn the set point of a jam by: a) watching as a jam cooks: it begins with a fast high boil and often reaches the top of the pan. As the water evaporates you may notice, after several minutes, the level of the jam recede once the viscosity of the liquid prevents it rising as high. This indicates you are making progress! b) then look at how the bubbles break on top of the jam as it reaches set point - they tend to hold for a little longer and are often swallowed back into the depth before you see them break. They seem almost 'lazy'. c) watch how the liquid falls from the spoon or spatula you are using. It starts quite watery and may drip off at several points of the spoon/ spatula. As it becomes thicker, the number of stream and drips reduce and the liquid coats the spoon a little bit. a) at this point, do the set tests (I tend to leave the jam boiling). Have at least 2 plates in the freezer ready to rock. Make sure to stir the jam with the spoon and then place a small amount on the plate (about a tsp will do) allowing some room for a second or even third test. Tip the plate on its side to allow it to spread and perhaps even wave it about to aid a quick cool (you may notice condensation form on the plate - give it a wipe with a dry cloth before a subsequent test). If, as you draw your finger through the jam, a noticeable 'bow wave' with some wrinkles form, the jam is set. If only a 'bow wave' forms, give the jam another 30 secs to 1 min and try again. If you think it is well overset, pour a couple of teaspoons of water in and test it. Leave the jam to cool for perhaps 5 mins and then place them in the sterilised jars (this allows the jam to set a bit so the fruit doesn't all float to the top). If the fruit floats noticeably, stir it with a dry sterile spoon after a minute or two. I have read several comments stating that the jam did not set and was reboiled after it cooled. This will cause a sharp decrease it the quality of the jam, so it is better to get it right first time! Try an easy jam like raspberry or black currant to begin with if you are a beginner or you are really browbeaten by more difficult fruit jams. I'll happily elaborate on points I've made or other aspects of jam making if anyone has a question.