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?
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.
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 flexing to the match the chocolate instead of holding rigid and releasing properly. This would explain why the problem is greater in the center of the molded chocolate. - That is the most flexible part of the mold.
I ordered some business card molds and had the same 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?
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.
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.
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.
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