Chocolate sticking to molds

I've been having an intermittent issue where my chocolate sticks to molds. It will always release around the edges but the middle (sometimes a large area, sometimes a small area) sticks to the mold. When I let the chocolate sit overnight, usually the surface is dull, but it snaps and appears to be tempered properly.

I think I've discovered that the temperature of the metal trays I'm placing the molds on influences whether this occurs or not. Has anyone else experienced this? What is the ideal temperature to keep my trays at when placing my molds onto them. I'm using custom food grade pvc molds and my bars are rather large at about 7.5 inches x 3.5 inches. Thanks in advance!

updated by @russ-apotheker: 04/09/15 05:46:53PM

Temperature can definitely be a factor, but so can humidity. Hot, humid days make molding chocolate difficult. It could be that the molds aren't cold enough, though. If necessary, after you have poured the chocolate, put them briefly in a temperature-controlled refrigerator to harden completely, and don't try to remove them before they are fully set. The larger bars mean you need more cooling time. Don't freeze them, though! You should be able to keep the trays at room temperature while filling them (as long as the room isn't too hot!) Then cool them, so that the chocolate can pull away from the edges.You don't want the trays cold from the start, because the chocolate will harden too quickly at the bottom, and warm chocolate will spill over and solidify around the edges making the bars stick. You want the bars to cool evenly.

I mould 75% of our products and our moulds are relatively deep. I often have the same problem as you. In my experience almost all imperfections are caused by inability to cool properly. Crystallization created heat, and that heat gets trapped by the mould. At least this is my current understanding. I'm always wondering if i should heat or cool the moulds before filling.Both seem to work, but not always...

According to Callebaut, moulds should be as close to room temp (20 C) as possible, but they also recommend slight preheating. So, around 25 C?

They go on to say that cooling is best done at 10-12 C, followed by time in the fridge. Circulation during the cooling phase is important, although this winter when it was between 10-15 C in my workshop (there is no heating in this country lol) I rarely had blemishes even though I had no special ventilation so I'm thinking at that temp as long your 10 C space is not too small, you'll be fine.

Source: http://goo.gl/BIjVFC (first result, PDF format)

From my limited experience...

Flexibility of the mould can also lead to uneven release and cooling marks. I noticed this especially with large moulds with flat areas without much detail. As the chocolate shrinks back from the mould it releases on the edges and corners ok: there it cools first and the mould is more rigid due to it's shape. The middle of the chocolate is the warmest and solidifies the last, but as the mould flexes with the shrinking chocolate it doesn't release well or stick. When this happens to me, the chocolate will still release hard and shiny (sometimes I have to give the mould a quick tap to release), but you see visible cooling marks where the chocolate released in stages.

I can imagine better cooling will help too. But as I can't control my cooling very well, I don't know to what extent.

Do you know how your moulds are made: injection moulded or vacuumform and what is the material thickness? How complicated/intricate is your design?

I prewarm my moulds just above room temperature, that seems to give better results. I cool at 8-10degC with the moulds slightly raised, so air can circulate all around. On the 'to-do' list is to put a fan inside the cooling fridge, to see if forced air circulation gives better results. Now it can take some time (hours) before the whole piece has cooled sufficiently and the middle finally releases from the mould.

Thanks all for the response. It definitely seems to be a temperature issue we are battling with. Unfortunately, we work in a shared kitchen so there are a lot of variables out of our control.

What we are finding out though, is if we put a wax paper liner down on the metal sheetpans just before placing the mold on it that it seems to give enough of a buffer that the mold fully releases. Don't ask me why that's working so well but it has thus far!

You need to pre heat the molds to your usage temp of your chocolate to avoid shock then you should get contraction and release if you are in temper.


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Jim Greenberg, Co-President
Union Confectionery Machinery Company
Jim@unionmachinery.com
www.unionmachinery.com

What's the best way to pre heat molds? We haven't tried that approach yet.

Russ -

The least expensive way (depending on the number of molds you have) is to use a dehydrator, which will also make sure your molds are perfectly dry. Believe it or not, Cabela's (the outdoor gear store) offers some good-sized ones that are remarkably inexpensive. Set the temperature as close as you can to the working temperature of the chocolate as Jim mentions.

Another option is a used proofing cabinet - just make sure that you don't hook up the water. You can usually find used proofing cabinets in a local restaurant equipment supply house that deals in used equipment.

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clay - http://www.thechocolatelife.com/clay/

I'm suspicious about the "need" to preheat moulds. I moulded chocolate all Dec and Jan at 10-15C temperatures, never preheated any moulds, and it worked great. Using Belcolade 73% dark.

Now that it's 25C+ where I'm working I do one mould, then watch it as I start the next. Once it starts to look like it's firming up in spots, I put it in a bag, and then into the fridge for 10 minutes. Then I take it out again and let it sit for at least another 10 minutes. Again, no preheating.

Another thing I've found is that moulds have to be 100% clean before you put anything in them. I use a high cocoa butter chocolate which is probably not the best for moulding and it makes a mess of the mould no matter how well tempered it is. Chocolate comes right out looking great but the butter it leaves behind will ruin the next batch if I don't reclean it.

I would also say you can make your own with an old fridge, or even a cabinet/box/etc. Put a lamp or other small heat source inside. Get yourself an STC-1000 to control the temperature. There are lots of people using these for beer making, etc. Google it and you'll find how-tos for using temperature controllers. It's like a 20$ device :D

That's an interesting thought and certainly not beyond the realm of possibility that our molds aren't squeaky clean. I agree too that I dont think it's the temp of our molds as we've made chocolate in various temps and it always comes out fine in our first round of batches.

It's odd though. We set our molds on metal baking sheets on a rack in a walk-in fridge and when we pull them out they've fully released. We generally do two rounds and the first round always goes perfect. The second round is the one that gives us issue and the only variable is that we re-use the metal baking sheets. We've tried letting them sit out for a half an hour or sometimes an hour to get back to room temp. We've also tried warming them back up on the stove tops ever so slightly. But the only thing that's consistantly prevented the second round from sticking is putting a sheet of wax paper between the molds and the metal trays on the second round.

Must be an issue with the temperature of the metal trays? Maybe the wax paper creates enough of a barrier to prevent the chocolate from setting unevenly....

Thanks Clay.

Do people ever use proofing cabinets to set their chocolate? Right now we use a walk in fridge but would be curious if a proofing cabinet would do the same thing....

Since poo-pooing the notion of heating molds I have read that not doing so may cause the chocolate to 'stick' to the molds in such a way that they release nicely and look good but leave butter behind which is sufficient to mar the next round. Related experiment currently in progress...

Lee, I'm very curious about your results, I still haven't got a real clue to solve my sticking problem.

Someone advised me not to clean the moulds if possible, as the residual butter is supposed to help in the releasing of the next round. Confusing...

I too have had occasional sticking of pieces in a mold. Usually some will just fall right out, with others remaining behind. Banging the mold on the counter releases some more, but sometimes there are stubborn ones. I have tried cooling them an additional amount of time, but last week, by accident, I tried something more extreme, something most experts recommend against. Since I couldn't get the chocolates out and so had nothing to lose, I put the molds in the freezer, got distracted, forgot them for at least an hour. To my surprise and relief, the stubborn chocolates fell out in perfect shape. So, with some reluctance (because so many caution against it), I suggest that you might try the freezer as a last resort.

I should add that other molds filled at the same time as the problem ones released the chocolates without any issue. There are so many variables, so many possibilities, that I doubt we shall ever know the culprit for such random issues. The mold may be too warm or too cold. The chocolate may be untempered or overtempered. The mold may be too squeaky clean or dirty (some recommend not washing molds so as to leave a film of cocoa butter). Perhaps it's cocoa butter decorations that weren't properly tempered and so stick to the mold.

I can say with some certainty that I've never had a problem with molds beingtoo clean lol. Unless it's a weird shape, chocolate will always come out of a mold if it's tempered right. In my experience :-D

I am wondering how you account for a mold filled with the same chocolate at virtually the same moment can have one cavity that releases immediately and a next-door one that does not. I can't see how the tempering can be right for one and not for the other.

Sorry to take so long to return with results, been busy. However I can safely say that, for me at least, pre-warming molds is done in order to ensure cocoa butter left by the previous batch is liquid before new chocolate goes into the mold. As a liquid it becomes part of the new chocolate, whereas as a cool solid, it "sticks" to the new chocolate and doesn't integrate, becoming an off-color mark on the surface of the new chocolate once it leaves the mold.

Now that I've "discovered" this (after ignoring advice on pre-heating for several months lol) I do it with 100% of my molds and the dirty mold problem I had before has been solved 100%.

Are the stubborn ones at in the middle of the mold? If some come out but not others, to me that says your cooling process is not happening evenly.

Hi Clay -

I'm curious as to the reasoning behind warming the moulds. I understand that in this case Russ was having trouble with sticking, but are there other reasons to pre-warm, like superior shine or quicker release time? I have never pre-warmed my moulds and have not had problems, but some of my moulds have a better shine than others, even when using the same chocolate (i.e. it's unlikely that some chocolate is in better temper than another) and identical moulds.

If you do recommend pre-warming as a matter of practice, would a heat gun also do the trick?

updated by @tessa-morgan: 06/16/15 04:30:08AM

Read here (second bullet point) http://www.thechocolatelife.com/xn/detail/1978963:Comment:204165

As to the "how" ... Put it under a lamp? Hair dryer? I use a dish drier, thanks to having the good fortune to live in a country where they're so common I've never paid for one haha. Just be careful not to overheat, since you might warp the mold. Nevermind what it'll do to your tempered chocolate

Re the warming of molds before filling: Nobody in this thread has mentioned the difficulty of doing so if the molds have been decorated with colored cocoa butter. I would be very reluctant to use any method of warming in this case as I would be afraid I would melt the decoration. It would theoretically be possible to warm the mold to the working temp of the chocolate/cocoa butter, but (I would think) it would be very tricky not to exceed that temp.

Time to buy a warning cabinet/other box that's a stable 32C!

I'm making chocolates at home, using polycarbonate molds for the first time. Clearly many people recommend warming the molds with a variety of methods... I'm wondering whether placing them in a warming blanket or on a warming tray (lowest setting), or placing them in my oven using the "proofing" or "dehydrating" settings (very low temp) might work. Any thoughts would be welcomed, thanks!