Breathable Brew Bung Mold

prusaprinters

What are these?3d printable molds for home brewers to be able to cast their own silicone breathable bungs (also known as waterless bungs). These type of bungs are extremely useful for home brewers as they don't require a liquid to keep things out, thus making aging a brew a lot easier. Why did I make itI was frustrated with the breathable bungs I had ordered online as the gap between the lid and the top of the lip was big enough that anything could have strolled in and destroyed one of my brews.Available SizesThese molds are available from the sizes of 28mm - 45mm in 0.5mm increments. These sizes are the size of the middle of the bung and should make it easy to find one that will fit snug in your carboy/bucket etc. Silicone TypeI would highly recommend that you use food safe silicone as I won't be held responsible for someone using non food safe silicone and ruining a brew or themselves. I've been casting mine in Smooth-On Smooth-Sil 940 Platinum Cure silicone as it's food grade and easy to work with.For a 30mm bung I usually mix up about 40g total (A+B) and there is some left over but it makes it easier to get it poured without taking forever. Do I need special equipment?Other than your 3d printer and the required equipment to mix and pour silicone, I don't think you *NEED* extra equipment, but obviously if you wanted to have a bubble-less bung you would likely have the best results with a pressure pot, but it's not a requirement and I myself haven't used one for all of my pours so far. FAQHow do I print this?Look at the slicer based (cover photo) picture but you should be able to print the pieces as is but you should flip the top over so the tips are facing up. I've printed it on 0.3 mm layer and 0.1 layer heights. 0.1 would be fine and probably advisable if you have a dialed in printer as it will give you less lines in your finished casting without having to do any extra post processing. Doing more some extra sanding might help as well if you are so inclined.Do I need to make a mold box?No, I just usually put some packing tape around the outside/bottom so any silicone won't leak out. How do I pour the silicone in?Assemble the mold so all 4 pieces are together and I would also advise taping the outside just to keep it from possibly leaking. After you mix your silicone up based on the manufacturer instructions. If you don't have a vacuum chamber to pull out bubbles from the silicone, pour it from high up and towards the side of the center (I mainly try to pour between 2 of the posts) and just pour slowly so you get rid of bubbles while it pours.After pouring you can try to do the tap method which means you tap your whole mold with silicone on a flat hard surface for a minute or two to try to coax more bubbles to come to surface.I also would say try to not go much higher than the top of the lid when you fill it up as it is meant to be as close to level as possible. This makes it so the gases in your carboy/brewing vessel can still release without too much hassle (if the lid is too thick on your silicone bung it might make it harder to release the CO2 for example) How do I release the bung after the silicone is cured?I push up on all 4 of the nubs on the lid so it frees itself and then you can use something like a paint scraper or even a butter knife to push between the side pieces to pull them off the base.The next part can be a bit more annoying, but using the scraper or butter knife, insert it under the bottom of the bung and lightly push up. Do this for all spaces and eventually it should just lift off the base piece. This bung is solid! How does it breathe!?The mold is made so you can easily cut the lid with a sharp knife or a razor blade (whichever you have on hand). Simply put the mold back on the base and put the sides back on. Then with your knife simply cut along the top edge of the sides. You might feel the posts, this is fine and do not force it here. After you get most of the cut in remove the bung from the mold and cut a bit more till the holes are able to be seen when lifting the top lid flap a bit. You don't want to cut too deep but you should have a good buffer for mistakes. You're now ready to use the bung for a brew!