I was working with my chocolate and today it got thick after I prepared 8 pranlines mold. I blasted it with the heatgun and it was still thick when it reached 37celsius.
updated by @hilmir-kolbeins: 04/10/15 18:43:32

I'm not a scientist so someone might jump in here and correct me, but my uderstanding is this: chocolate can form many types of crystals as it sets. Only one sort is correct for "tempered" chocolate. For chocolate to be tempered, I think you only need about 2-3% of the chocolate mass to have the correct crystal structure. The issue is, these crystals grow/multiply and cause "untempered" crystals to transform into tempered crystals so that the 2-3% of tempered crystals will grow to a larger number. This is what occurs when the chocolate becomes over-crystalised.When you hit it with your heat gun, you melt some of the tempered crystals out, but they can still re-temper again over time if conditions are right.

The final temperature for tempering a chocolate is the point where the unstable crystals would be melted out. Best for the betas you want. But as mentioned by Gap, they continue to multiply. Taking you far above the 2-3% target of crystal fraction. Reheating is tricky and not a long term solution, just a quick fix for that last mold or two.Easier to temper just what you need, then add chocolate that was just taken down from 110-120F full melt to a couple degrees above temper and add it to the tempered paste to thin it back out. You need to find the point where you match your usage rate to the amount of chocolate always tempered, to the rate you can add new paste. With some practice you get a rhythm down that works. But equipment the wrong size put limits on.If you're just looking for a little more time each tempered batch, when you're tempered, hold a degree or two high with no mixing, just an occasional good stir to make sure temp is even throughout the mass. Mixing produces shear, promoting crystallization.

it could also be something as simple as the humidity where you are. Do you know what it is? If you're in Iceland it should be fairly dry in the cold winter, but I'm not sure how a lot of snow might affect that.If it's higher than 50% RH, try to install a dehumidifier or AC unit set on a comfortable temp which should also dehumidify.

I am adding a question to this older topic as it is more or less the subject of my latest chocolate issue.

I have been using Felchlin Maracaibo for dark and Valrhona Opalys for white. During the winter both behaved fine. For my Easter 2014 batch of chocolates, I was able to prepare several molds with the Opalys when it thickened up to the extent that there was barely any space for the ganache in some of the cavities. I raised the heat several degrees, and that did not appreciably help. This job was done at the beginning of April, not particularly warm or humid. A few days ago, the same thing happened with Maracaibo, and raising the temp even above 90F did not help. It wasn't quite as thick as the Valrhona had been, but for a dark chocolate, it was really viscous. This time we were experiencing some warm, humid weather--though I was running the AC to try to prevent the thickening.

On another forum a chocolatier from Richmond, Va. (about 100 miles from me) wrote that she had experienced a similar thickening of chocolate on the same day and attributed it to the humidity. She mentioned adding some cocoa butter.

So today, aware of the possibility of humidity, I turned up the AC full blast. I added cocoa butter to the Opalys, and it was perfect. My recently ordered hygrometer arrived, and revealed the humidity to be around 20-25%. So I'm thinking I may have found the issue. The problem is that it is not consistent (the first thickening of Opalys was not on a humid day). Tomorrow I'll be using Maracaibo and will try the same routine to see if it helps. I won't add cocoa butter, however, unless it turns out to be necessary.

My question relates to the humidity issue: Assuming that is the problem, is the chocolate I used on the humid days permanently "humidified" or will it return to its previous state once it is out of the humidity? I don't want to have to add cocoa butter to the chocolate from now on, nor do I wish to discard the chocolate.

Incidentally I was tempering the chocolate in a Chocovision machine. Someone at that company recommended raising the working temp for the Valrhona to the 90F range, but that seemed a bit high to me (Valrhona recommends 84F).

Thanks for any guidance.

Once your chocolate has adsorbed ambient moisture, it's very difficult to get it to give it up. You may be able to compensate by adding a little (0.05-0.1%) more lecithin to get it to bind up the moisture, but that only works to a certain extent. Prevention by keeping the RH low is the best medicine to cure this problem. If you can't prevent it, you may be able to make it better by adding lecithin. If that doesn't work, a high shear high temperature mixer can be effective to a smaller degree, but i'd keep that the last resort option, and you risk other damage via this method if your temperatures are too high.

Thanks for the reply, even though the news was not quite what I hoped for. When you speak of "adding a little (0.05-0.1%) more lecithin" I assume you mean a little more than is already in the chocolate. That's what I was concerned about--especially white chocolate always seems to have lecithin in it.

Yes. Lecithin is called an amphiphillic emulsifier, which means one end likes to stick to fat, and one end likes to stick to water. if your chocolate has adsorbed some ambient water, it thickens the chocolate by dissolving some of the sugar (even though it's a very small amount), and makes a syrup,, and as we all known, water (syrup) and oil don't mix - and it gets thick. The lecithin can 'bind up' some of the water in that syrup, making it 'slip' past the oil so it doesn't get thick - but if you use too much (hence the suggest to use vey small quantities), it can actually make the chocolate thicker. It's not a cure all by any stretch, but can help tweak viscosities when small amounts of moisture have been taken up.