One thing that always provokes spirited debate around the Hackaday bunker is just how dangerous is it to use 3D printed plastic in contact with food. We mostly agree it isn’t a good thing, but we also know some people do it regularly and they don’t drop dead instantly, either. [Jakub] decided to do some testing and make some recommendations. There’s even a video explaining the results.
Unlike a lot of what we’ve read about this topic in the past, [Jakub’s] post is well-researched and does actual testing including growing bacteria cultures from cups used for milk. He starts out identifying the EU and US regulations about what you can call food-grade. There’s also recognition that while a base plastic might be safe for contact with food, there’s no way to know exactly what additives and other things are in the plastic to change its properties and color.
The chemical makeup of the plastic is just one aspect of food safety. Another important aspect is the ability for harmful pathogens to lodge in the little voids and layers of the printed object. There are also the materials used in the printer. It is possible that safe plastic can be made unsafe in a dirty hot end or by contact with something noxious in the printer.
The gaps problem led [Jakub] to an inescapable conclusion: no matter what you print with, you’ll need to coat your prints to make them actually food safe. However, the coatings are not good for things like chopping boards or things you’ll expose to heat including microwaved food or hot dishwashers. If you think SLA resin might be better, he discusses the problems with that, too.