After reading through everything I could find online, I still can't find a solution to this strange issue I've been having with my chocolate temper. I'll lay out all the specifics and some pictures in hopes that someone, somewhere, has had the same problem before and can give me some pointers. Thanks so much!
Alright, I'm working with a Chocovision Revolation X3210 tempering machine (capacity 10 lbs). I've had this machine for just under a year and have had beautiful tempers out of it for months.
I use the default tempering process on the machine - it heats to 108 degrees Fahrenheit, I add seed (I use more chocolate from my box of Noel chocolate - I don't measure it, I just throw a handful or two behind the baffle) and it cools to 90 degrees Fahrenheit. I remove the remaining seed from behind the baffle, and the chocolate continues to cool until it reaches 88.7 degrees Fahrenheit. When it is finished, I stir the batch for a few minutes and do a test with my offset spatula.
The chocolate used is Noel 55% semisweet dark chocolate. I've been using this chocolate for over a year and have had good tempers with it in the past.
My kitchen is between 64 and 68 degrees Fahrenheit, and between 28% and 38% humidity. Outside, it's been wild weather here, with temps from 45 to 80 in the past two weeks, and it's been both bone dry and rainy. My chocolate kitchen stays consistent throughout the changes in weather (at least according to my inside thermometer).
What I've been trying to make for the past week or so is molded chocolate bars and chocolate bark. For the bars, I use plastic sheet molds that are approx. 0.5 inch deep. My technique for this is I ladle the tempered chocolate into the molds, scrape off the excess chocolate with a metal bench scraper, bang it on the table to release the bubbles, and place the nuts or fruit on top. I then set the mold on one of my aluminum baker trays, which I slide into my rolling baker rack. For bark, I ladle the tempered chocolate onto a baker tray line with a sheet of acetate, hold the tray sideways to allow the chocolate to spread thinly across the tray, sprinkle the nuts or fruit on top, and slide the tray into my baker rack.
I have been using these techniques for over a year with success. (I do notice that my chocolate bars sometimes are barely streaky on the side I scrape, but I don't see how I could avoid that. The excess chocolate does need to be removed, after all!)
The problem I've been having recently is what I have identified as chocolate bloom. That seemed to be the most logical explanation according to what I've read and what it looks like. It's basically a dis-colorization of the chocolate - it looks whitish and dull, with the occasional streak. This is happening on the side exposed to the air, not the side that touches the mold or acetate. That side looks beautiful - shiny and completely free of any dis-colorization or streaks. The chocolate is hard and has a nice snap when it's broken. It does not melt in your hands and does not feel soft. It seems to be in temper except for the dis-colorization on top.
To me, it seems this must be the cause of the chocolate cooling incorrectly - either too slowly or two quickly? I wondered if maybe it is falling victim to some sort of draft from either my air conditioner or two dehumidifiers, but I placed the molds and bark at various places around the room and had the same ending product. The strangest part is that my test on my offset spatula looks wonderful.
I am stumped. Has anyone ever had this happen before? If so, how did you solve it? Would blowing a fan over the cooling chocolate help? Should I pop the cooling chocolate into my refrigerator for a few minutes?
Any suggestions or comments are very much appreciated.
Please excuse the poor picture. I left my camera at home and had to take a photo with my phone. I shall upload another if you like. :)
It sounds like you need to cool the chocolate down quicker. If it's not quick enough some of the cocoa butter molecules in the warmer center of the chocolate slowly release and rise to the surface. You may also want to experiment with using layers of chocolate to fill the mold instead of just one pour.
I'm with Adam G on this - as chocolate cools the latent heat of crystallization given off by the rapidly growing crystal lattice can warm the chocolate considerably and throw off the temper. As soon as you see the chocolate starting to crystallize around the edges, put your molds (or your bark) in the fridge (ideally with good air circulation) for about 10 to 15 minutes. Don't forget them in there or your next problem will be sugar bloom from condensation.