Mold Release / Ring Formation Issue in Mold

We have a new square mold we've been working with and it's causing me some grief. Upon release there is a round mark within the chocolate. See the pictures.

This round/spherical look doesn't start showing until near the release stage of the mold. We checked it at 5m intervals and it's as if the chocolate's retraction from the mold is creating this look.

When colored and detailed you can't see it unless you're looking for it. But on a plain piece of chocolate it shines through pretty well.

You can see it even leaves the ring within the mold. We polish it out and it comes back the next time. Nothing we did seemed to help obviate it.

We did 500 units of these and about 85% of them showed this type of mal-detailing.

Anyone seen this before?

updated by @andy-ciordia: 04/10/15 08:39:29PM

I have a square mold that is smaller and deeper than this one but has a smooth top and I run into the same issue. Unfortunately, I don't have a good solution for you since I've never figured out a way to stop it. For a while I thought maybe it had to do with the ambient air temp, humidity, and cooling time of the chocolate. I also polish my molds before each use but the marks keep coming back. I find that molds with a large flat surface on what is the top of the chocolate usually have this issue and I've opted to avoid these types of molds.Maybe someone else has a great solution to fix this problem, but you are not alone and I don't think it is any kind of defect in the mold and I highly doubt it has anything to do with the temper of your chocolate or cooling times. Sorry I don't have anything better to offer.Andrea

Andy -

These look like thermoform molds. Right?

One possible culprit is that the molds are the wrong temperature, likely too cold, and things are cooling down (too) unevenly.

Try warming the molds (to within a couple of degrees of the chocolate - experiment; a couple of degrees either may make a difference) and make sure the room is not too cold. Also check your airflow. If there is none, try blowing some air past the molds to remove the heat more evenly and efficiently.

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

I have a theory on this but haven't ponied up the money to try & fix it.

My theory is that as the chocolate is cooling and retracting, the flexibility of the mold is flexingto thematch the chocolateinstead of holding rigid and releasing properly.This would explain why theproblem is greater in the center of the molded chocolate. - That is the most flexible part of the mold.

I ordered somebusiness card molds and had thesame problem.

My idea to fix this is to get some food grade epoxy or other acceptable rigid material and apply it to the back of the thermoform mold. However food grade epoxy is not cheap and I'm not ready to drop the funds on that experiment. I wish they made business card molds from polycarbonate! They would be worth every penny.

The reinforcing options I've looked at include:

Food Grade Epoxy - i.e. http://www.masterbond.com/certifications/food-grade

Silicone to be molded - i.e. http://www.makeyourownmolds.com/

gluing an aluminum or stainless steel bar to the back of the mold. i.e. run it across the center of the square. This would hopefully reduce the flex of the center.

What other materials can you think of?

The one I have an issue with is a polycarbonate mold, so not sure if your idea would work or not. Probably worth a shot with the more flexible mold when you feel like spending the money . Clay's suggestions are definitely a cheaper way to go. I've tried using my mold in various conditions and have gotten the same result. Luckily I didn't buy loads of this mold and don't feel bad setting it aside for ones I don't have an issue with.

Interesting thoughts... Yep, these are thermoform. Picked up 10 for a project. We've got other thermoform moulds though that are large--not this square--one is a 4"x1.25" and we don't see it happen there.

You can definitely see it begin as the chocolate cools and naturally pulls back the last held contact point is that circle/sphere.

Now that the project is past I'll try your suggestion clay about temperature as they were definitely not warm but at room temp (69-70'). In a production run if we were airbrushing I don't think we could keep them warm since the cocoa butter would not be setting-- but for a test its definitely viable.

Since the epoxy would be on the back of the mold--not touching the chocolate--would it actually need to be food-safe epoxy? That being said, I believe there are lots of inexpensive epoxies/glues that are food safe after curing--J-B Weld and Gorilla Glue both are, for example.

I use thermoformed molds for my bars and usually get these marks, too. But, I have had times where the marks were either very small or nonexistent. I haven't been able to figure out the exact process to minimize or eliminate the marks, but it seems to be a combination of well (perfectly?) tempered chocolate, warmed molds and good cooling.

I'd be interested to see if Larry's idea of reducing the molds' ability to flex would help, too.

Dear Andy,

How do you cool the chocolate? In a fridge? Perhaps some additional airflow could make a difference? The centre is also where the last heat is concentrated and a active airflow could be of help to reduce quicker the temp of the core of the chocolate?

Best and success

Rodney Nikkels

Amsterdam

I am currently having the same issue with my chocolate bar moulds, temperature of the tempered chocolate is correct, tested it on back of palette knife and the chocolate sets hard with no streaks, yet when it comes out of the mould I get these light swirls just on the centre of the bars. After reading this I warmed the moulds before pouring, and also increased airflow with use of a fan and some cooling racks for setting, room temp is about 20degrees C so not too cold, yet I am still having the exact same issue. Also tried various cooling methods such as total set in fridge, total set at room temp, mix of fridge and room temp setting but still same outcome. So I now agree with Larry and think it could be because unlike poly moulds, my thermoformed moulds are more flexible and so are actually flexing with the contracting chocolate and leaving this middle circle bit (that doesn't flex) to set differently. Will try strengthening the moulds today and will report back with my findings.

James - thermoformed molds are known for this, and the problem is exacerbated if your mold has long, flat surfaces. I have both types of molds (those and poly), and as far as I can tell it's just about impossible not to get release marks with the thermoformed molds. If you figure out a fix for this I would be fascinated to hear it, but I suspect the only realistic solution is the obvious one.

As frustrating as it is, i fear i am going to have to admit defeat to the release marks on my chocolate bars and simply make do for now. I reckon i have tried everything now, from various different methods of cooling, to warming the mould first at different temps, and finally today i got round testing out the theory of strengthening my thermoformed mould with a metal bracket on the back in the hope that this would fix the issue. sadly it hasnt. The most annoying thing is i still have no idea WHY it leaves this mark on the chocolate, my square bars are only 8cm x 8cm, but obviously this is a big enough flat surface like Michael says to be an issue. Any extra ideas would be very welcome.....

It is the 'big' flat surface. 8 by 8 cm flat is sufficient to cause a problem with a thermoformed mold which contracts differently than metal or polycarbonate.

You can make the whole surface look the same (however it will be matte not shiny) by using a badger hair brush (or my personal less expensive option - a Japanese varnish brush from Lee Valley). I suppose you could try polishing with ice water as well.

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www.eztemper.com

www.thechocolatedoctor.ca

Hi Kerry,

I will try the different suggestions, although i may just end up leaving it with the weird cirle in the centre for now as the rest has a nice glaze, until i can afford some polycarbonate ones to be made.

You could make a nice thin transfer sheet under chablon piece and place it over the marks.

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www.eztemper.com

www.thechocolatedoctor.ca

I read the whole thread, I have the same problem (see attached), namely: weird circle that can't be avoided, happened in all the chocolate colors always, and of course doesn't exist in polycarbonate moulds.the dimentions are: 5*5 cm.

Bottom line: I have to live with that? I'm currently make an "internet research" to try to find out if there is something I can do...

Very sad to invest 600$ and to get not a perfect item:(

I have this problem, too, but only on the thermo moulds. My theor is that the flat surfaces are less rigid and don't release well. What i currently do is use a heavier gauge mould when i get them made. I think the standard mould is 40 gauge. I spec 60 gauge for moulds with flat surfaces. 

To minimize this, try have the moulds at 80 degrees and the room at 68. I crystallize at 55 degrees. 

Cheers.

Hi Daniel,
I tried in the last two weeks couple of things, namely, heating the moulds, trying to mould single cube and so on, nothing helped.
I have 1mm and 0.5mm thick, but the moulds are too big, i.e 25*25cm so they won't be rigid anyway.
I should assume I need to learn to live with that?

I can assure you this can happen on polycarbonate molds, I spent a few good years trying to get rid of them! My theory-It is basically the heat in the bars last stand, If you have long flat surfaces the chocolate cools, shrinks- releasing heat and this collects in the middle of the bar. I would not recommend any physical cleaning of molds as they do in fact scratch up, wash in dishwasher with a good non filming detergent. When we did photoshoots I used to make bars with undertempered chocolate  and then freeze them came out LOOKING beautiful.

Hi,

I assume that your theory is correct sometimes and not always, when I mold 1 kg of chocolate to flat aluminium vessel (thickness of approximately 1 cm or a bit less) no releasing marks..