I'm in the process of making sugar wax made of heated sugar, lemon juice and water. I have found a ratio that works great when it's heated up to 119 C (246.2 F). It gives me a wax that has the perfect consistency and firmness. The problem is that this ratio and temperature works fine only when making one jar of wax. When I try to scale the volume up (using the same method, recipe and temperature) it turns out different. The more I scale it, the more runny it turns out even though it reaches the same temperature. I'm using the stove (electric) to heat up the wax. I've been consistent with using the same pan and same temperature setting for the stove every time I make the wax. I'm trying to understand what is happening when combining these three ingredients. Why do I get a different consistency when increasing the volume? (even though I'm using the exact same recipe and reaching the same temperature). What are the parameters that play an important role? Until now I've thought that the volume (as long as the ratio is the same) doesn't matter, as long as it reaches the right temperature. This turned out wrong, and now I'm interested in knowing what is causing it to turn out different. Does anyone have any experience of something similar? Maybe there is some chemical theories I'm missing? I would appreciate all the help I can get. Thanks! 
I will throw out a suspicion, although I am not certain that it is the correct one. What you are doing here is to create invert sugar with the lemon juice - if you didn't use that, you would end up with hard candy, not a malleable substance. The acid in the lemon is not an ingredient in the reaction, it is a catalyst. So I wouldn't wonder if your scaling up means that you get a higher proportion of the invert sugar, making the whole mass softer. If my theory is correct, you should get something closer to the desired result by scaling up the sugar and water, but keeping the lemon juice the same as in the original recipe amount. "Something closer", but not exactly the same, because while the acid will be the correct amount without scaling, it might need longer time to create the same proportion of invert sugar in the increased mass - but you cannot really give it more time, since you are restricted by the maximum temperature reached by the sugar syrup. So in the end, if you want the exact same result, you will have to find out empirically exactly how much lemon juice you need. But as things stand, there is a good chance that using the unscaled amount will be a good starting point. 