If you are going to be working with chocolate on an ongoing basis (ie all day), then you need a piece of equipment that will continually agitate the chocolate when it's in temper. The size of the machine will depend on how much chocolate you need to temper throughout the day. We currently use two different types of machines in our shop - Pavoni Mini-Temper machines for hand dipping (holds and agitates about 10lbs at a time), and Savage 50lb tempering kettles. Both are semi-automatic, meaning they cycle through the temperatures for your chocolate, and can be programmed to make tempering almost dummy proof. The Pavoni's are fabulous for that and completely automatic, whereas the Savage machines require manual intervention at certain points, but trigger a buzzer when each point is reached. Each Savage machine (we have 2) will easily temper 100lbs of chocolate every 8 hours.
In my opinion, if you are working with chocolate all day, you need machines that will step through the tempering cycle for you, and continually agitate the chocolate. This will allow you to do other things, instead of standing there, stirring, and babysitting your chocolate.
They are good people to work with. I second Brad on the Savage. Love them!
Mol d'Art melters do not help you temper your chocolate. What they do is keep the chocolate at a precise temperature to keep it in temper once YOU have tempered the chocolate. With a Mol d'Art melter, you do the stirring and you are in control regarding the temper - no beeping with this machine.
What I do is melt my chocolate overnight at 45 Celcius. The next day I turn my melter off and remove the pan to my stainless steel table. The only reason you need to take the pan out is to make the tempering process faster. You can keep the pan in the melter if you'd like. By removing the pan, I need to add less seed. The reason this can be a good thing is to keep the viscosity of your chocolate more fluid. I add seed and stir it in. I then do other things and stir it every few minutes just a little. If you want to stir more at this point it won't hurt a thing. Add more seed as needed. The lower the temp. gets, the less seed you add. Wait until the seed is melted out before adding more. When the temperature reaches 34 C, I give it my full attention. At this point, you don't want to add a lot of seed. Add just a small handful and stir. Stirring is key at this point to develop beta crystals. Tempering means you are developing beta crystals so you can't just let it cool without any seed and/or agitation. When seeding you don't have to worry about doing much stirring when the chocolate is hotter than 34C. The beta crystals melt out above that temp. so adding seed above that temp. is essentially just to cool it down. In total, because I remove the pans to a table, I only use approx. 10% seed.
Unfortunately, the chocolate will continue to get thicker the longer it is held in temper in the Mol d'Art. Use a heat gun and play with the temp. gauge as needed. If you have a larger melter it will keep the temper better. You will find that tempered chocolate in a wheel tempering machine will continue to thicken as well - 'tis the nature of the beast! However it will do so to a lesser degree as it is being 'stirred' continuously and has a much larger volume of chocolate. I turn up the heat on my Mol d'Art if it starts to thicken. I play with the temperature gauge constantly. At approx. 1 hour after I start dipping I start to turn up the dial slightly. The timing is arbitrary - I start to turn it up when I notice it starting to overcrystallize. Don't wait until it's as thick as peanut butter. It's amazing how a slight increase in temp. will keep the crystals under control and keep the viscosity constant. I do periodic temper tests to make sure all is well. As long as the temp. stays under 34C I don't worry about it.
Another tip - make sure you set your working temp. high enough to combat over-crystallization. Because smaller amounts of chocolate over-crystallize faster than larger amounts of chocolate, if I had to do it over again I would buy bigger melters - the 12 kg. But that being said, working with the small melters has given me great experience with the challenges of chocolate!
Best of luck with your decision Salome.
Lana, thanks for your comprehensive response,
There is one more thing I'd like to know: how long does it take Mol d'Art melting machine to melt about 3, 6 or 12 kg chocolate?
It's almost a year since you posted this question so I assume that by know you are an expert at this. Typically - assuming the chocolate slab is new, the machine is pre-heated for a few minutes and the slab is cut in small pieces (tiny bits like buttons) - a 1kg batch should not take more than 10-15 minutes. This is very open-ended as many variables need to be defined (not to mention how patient one is) but that time frame is a reasonable figure to start with.