I have had some hit and miss tempering with the prototype temperer. It worked beautifully for my smaller test batches and only tempered half of the large batch I made last week. I have been looking at all the tempering methods you talk about on the website and contemplating trying it without the tempering machine. I know when I have done it at your house, we did hand tempering by using a double boiler and ice water bath. I would assume the same temperature parameters apply there as with the temperer: Get the chocolate down to 82 or so, then bring it up and hold it at 88-90.
I also read the tempering page on the site again and it discusses using marble and working the chocolate. Since i do not have a marble slab, this option is out.
Then I read your instructions on tempering in the santha using seed chocolate. That one is looking like something I want to try.
What do you recommend for me?
First off, everything you try without the tempering machine is just going to be harder. Even if it does not control the temperature right where you want it, you can use it to control the temperature manually and it stirs. That is basically it's benefit. So your assumption that the same temperature parameters apply are spot on.....except they are not absolutes. If you are a couple degrees too hot on either end, you can loose temper. So it might be than simple.
For the larger batch that only partly tempered, which half was it. The first or last half? Or was it peppered throughout?
About the only thing we know for sure is that you brought it down cool enough to form seed chocolate since some of it tempered.
If first, then I suspect you didn't turn the heat down and it over shot for the 2nd half and you lost temper.
Or it could also be handling technique.
If the 2nd half or mixed, then it could be handling technique.
What I mean by handling technique is over working the chocolate. Extra smoothing. Lots of dipping to fill one mold. And it sometimes gets worse near the end as the chocolate starts to get thicker. If you notice it getting thicker, then the chocolate is tempering (crystals are forming) and you have to raise the temperature a little to keep it fluid. It can sometimes be like walking a moving tight rope. Where at the beginning your working temperature was 87 F (for example) but by the end, it may be 90 F to keep it fluid enough to work with. Why can't you just have it at 90 F to start? Because the temperature is related to the amount of temper (i.e. the amount of type V crystals) in your chocolate. The more type V, the higher you can and need to go to keep it fluid. And you tell how much is there by viscosity. Basically, as it thickens, raise the heat to keep it in balance. You are destroying some of the type V, but that is ok. There is plenty, as noted by how thick it is. If you don't raise the temperature, then you have to 'work' the chocolate and you mess up the crystal structure, and you get bloomed chocolate.
Next. Marble. It isn't magic. It is often mentioned because it is non-porous, easy to clean and a good heat sink. I have used tile, granite, Corian and even just a clean counter. About the only thing really out would be wood or tile with grout. So anything that has those properties (glass? sure) will work.
As for working with the Melanger and seed, if you have a tempering machine, then in a way you are going backwards. A melanger is for when you don't have something that stirs slowly and mixes the chocolate (like a tempering machine) and for the sake of using something that you have on hand. The melanger has no other benefit, and has drawbacks. It runs pretty fast. The rollers get in the way. You have to add external heat. If the control on the tempering machine isn't working, then don't use it and add external heat and an external thermometer. Or better yet, use the tempering machine, use an external thermometer, verify what it is seeing on the display is what you are seeing from another thermometer, and if in doubt, use the external one and adjust your tempering machine settings accordingly. If your tempering machine says it is 89 F, but your external thermometer says it is 91 F, you can see the problem. Reduce your tempering machine temperature a degree or two (assuming it's smooth and has a low viscosity of course).
So what I suggest if finding out the cause of the hit and miss tempering. Stick with the tempering machine, and find the pattern as to where it is not working...then fix it. As I see it, it can only be a couple things. Either your chocolate is getting too hot, too thick or you are handling it too much....or some combination of those.