Question about making food molds

Discussion in 'Materials' started by icarael, Mar 23, 2016.

  1. icarael
    icarael Member
    My girlfriend and I were wanting to make a 3d printed chocolate bar shape so we can make a food grade silicone mold. What would be the best way to create the 3d print so that we would not need to sand or modify the model so much after it is printed. We would also be using a sealant on the model to plug up any pores and such when we make the silicone mold as well.

    Thank you for your help, I attached a picture of the 3d model we were looking to print.

    Attached Files:

    joetlnf likes this.
  2. draw
    draw Well-Known Member
    Good question. I'm waiting on a mold master to come back so I can try this myself. I have a chocolate bar shaped mold in my store that I hope to try out later this year. I put a thin flange around the bottom edge so it can be better glued down to a base in case there is any warping of the bar. I might be able to thin the walls a tiny bit to reduce cost but the top surface is thicker to allow engraving with the customization tool. If you have a fixed pattern you can probably thin the walls to 1mm and not have the thing warp under pressure from the molding process but this might depend on the type of silicone used.


    I plan on using white strong and flexible since it is cheapest, maybe get the polished material, and seal it with a clear acrylic spray. Glue it to a base, form walls around it with plastic or clay (not sure), spray with mold release, and then use a two part silicone mix to pour the mold. There's a lot of information on the web as to how to do this so more research is needed. I still need to finalize plans and pick out a silicone.

    This is the mold master I'm waiting to get back right now. It's large enough to make a chocolate with an Oreo in the bottom but it might need to be one of those new slim Oreos. I hope it works. If the chocolate thing doesn't work out I can make some fancy hand soaps.


    joetlnf likes this.
  3. joetlnf
    joetlnf Member
    Did either of you have any luck with this? I'm trying a similar thing with chocolate molding and want a nice smooth finish for a glossy chocolate surface. I ordered a part in the strong white flexible (polished), which looks great, but is pretty porous, making it difficult to cast with silicone. I also know that the porosity will give a rough appearance to the chocolate.
    draw, have you tried the acrylic spray? icarael, any luck with your application?
    I'm considering trying again with PLA and then doing an acetone vapor polish, but want to exhaust options with the strong white flexible first, since it has nice definition and is the cheapest.
  4. 8_Perf
    8_Perf Well-Known Member
    I think its great that everyone is jumping in feet first and going all out with 3D printing everything they can get there hands on, but as a classically taught, old school, model maker, I have to ask................Why not just mold a real chocolate bar? Your pattern costs you less than a dollar if you shop wisely. Having one printed could cost upwards of $20 or more, and then you still have to prep it. I don't understand. 3D printing is a great tool, but just because its new and shiny, doesn't necessarily make it the best option for a job.
  5. joetlnf
    joetlnf Member
    8_Perf, for a basic chocolate bar shape, going out and buying a pre-made mold is obviously the best option.
  6. RudyLime
    RudyLime Well-Known Member
  7. joetlnf
    joetlnf Member
    Thanks, RudyLime, I've dropped Jena a note.
    I've also ordered some XTC-3D and Smooth-Sil 940 and will give those a try, since the XTC-3D apparently won't interact or leach into the Smooth-Sil when fully cured. There are other food-safe, low viscosity epoxies available from other vendors and I might give those a shot as well depending on how this goes...will post results when I get them!
    RudyLime likes this.
  8. draw
    draw Well-Known Member
    I have not yet used my mold master to cast anything nor have I prepped it yet. :( But it looks nice!

    Molded bars @ 22 minutes.

  9. RudyLime
    RudyLime Well-Known Member
    Hey @joetlnf, did you hear back from Jena?
  10. joetlnf
    joetlnf Member
    Yes, she recommended using a spray on epoxy for those who need good uniformity, but that for her needs she rubs on a layer of Vaseline.
  11. RudyLime
    RudyLime Well-Known Member
    Cool! Well be sure to share the results once you're ready!
  12. joetlnf
    joetlnf Member

    I ended up using XTC-3D to seal the mold (printed using Shapeways strong & flexible plastic), and Smooth-Sil 940 to cast the final chocolate mold from that. I haven’t yet had a chance to temper and pour some chocolate, but I’ll post an update when I do.

    A few things:

    1) The XTC-3D does pool a bit in the nooks and crannies of your model, so I suggest following up with a dry brush or sponge to mop up excess. You can also dilute the XTC-3D using acetone if you want a thinner coat – I haven't tried this, and it lengthens the cure time.

    2) The detail on the model will transfer almost perfectly to the silicone. This includes the finish. So, if you have a nice shiny finish on your model then you will have a similarly nice, shiny finish on the silicone mold. I mention this because if you choose to sand the mold using fine-grit sandpaper after applying your first coat of XTC-3D (I used 400 grit), you should follow it up with another thin coat to get a uniform shiny surface. I did not do this, so there are patches of matte finish where I sanded mixed with glossy where I didn’t. It doesn’t look bad, but it could be better.

    3) I did not use any releasing agent on the surface of the model before pouring the silicone, and that ended up working out fine. However, if I’d thought ahead, I would have designed my model a bit more wisely to help out: angled instead of vertical sidewalls on the lettering, and a lower aspect ratio in areas where spacing gets tight (e.g. between the bottom of the “J” and the boundary).
  13. joetlnf
    joetlnf Member
    As promised, here is the final. Besides the tempering of the chocolate, which did not go particularly well, and the mix of matte and shiny finish, I think the results are pretty good and the process should work fine.
    There are some bubbles, which probably could have been removed with more vigorous tapping of the silicone mold.
    And with respect to the finish: as I mentioned above, it is the same as the mold, which is the same as my original model....the patches of matte finish were caused by sanding the XTC 3D to level out the surface, and should be easily fixed by applying another thin layer of epoxy on the surface of the 3D print before casting the silicone.
  14. joetlnf
    joetlnf Member
    I figured I should post an update. I ended up 3D printing a new bar (strong white flexible), finishing using the process described above (XTC-3D), and then casting using Smooth-Sil 940. We now have a number of silicone molds that we use to cast our bars, some results are shown in the images below.
    Though silicone will initially release well from the finished print (it doesn't adhere much to the XTC-3D), it does contaminate the surface of the epoxy over time so that mold release becomes more difficult with each subsequent silicone mold that you cast...and after a few castings, the silicone tears when you try to separate it from the print. You can get around this by using a mold release agent like a wax paste. Wipe it on and buff it off the 3D printed master, then give it some time to let any solvents evaporate off (otherwise it can contaminate your mold, and possibly your chocolate as well).

    JJ_pouring.jpg JJ_bars.JPG
    Last edited: Apr 27, 2017
  15. 8_Perf
    8_Perf Well-Known Member
    What brand of rubber are you using? Smooth-Sil 940 from Smooth-on is a food grade rubber. I wouldn't think it would need a mold release for something like chocolate.
  16. joetlnf
    joetlnf Member
    The mold release is for separating the silicone mold from the 3D printed master (which is shaped like the chocolate bar) after the silicone has set.
    There is no problem releasing the chocolate from the silicone mold.
  17. Dream3d
    Dream3d Member
    It would be great if shapeways could introduce silicone as a new material, only for molds. I know the mold making process is quite simple if the mold master is modeled properly, but in some countries quality food grade 2 component silicone is impossible to get :(
  18. joetlnf
    joetlnf Member
    ...or if Shapeways could provide a finishing service (e.g. epoxy) for some of their porous prints, that would save folks like me a lot of time. With some R&D I bet they could figure out how to do it at high quality and relatively low cost.
    Dream3d likes this.
  19. Nyeusi_Tech
    Nyeusi_Tech Member
    would using a metal, ; like aluminum work better? About to try this something like this and want to avoid headaches...