Often one of the first printed projects people create on their freshly built or purchased 3D printer is some sort of cup or shot glass. But as this thingiverse blog points out:
Just because you can eat food out of it, doesn’t mean it’s a good idea.
While plastic is often seen as this inert, sterile material. It will break down under the right conditions. Those conditions vary from plastic to plastic, with some plastics taking such a long time to decompose they sometimes draw analogies with nuclear waste.
So what about the common 3D printing material PLA? Does that break down? Does it release nasty things as it breaks down? Should you really be using it in contact with food?
An article in the Smithsonian magazine outlines two of the main selling points behind PLA:
- It is a bioplastic derived from stuff like corn, potato and tapioca. Compared with ABS, which is a more traditional plastic derived from oil.
- It is compostable, throw your failed PLA print scraps into a compost heap that is hot enough and it will break down into delicious humus for your plants to eat. I have never been game to try this, because I had no idea what other things might be lurking in the plastic.
OK, so PLA does break down. If you put food in your PLA, what migrants (a polite term for saying parts of the plastic) might find their way into your food?
Fortunately a bunch of clever people ran an experiment titled the Safety assessment of polylactide (PLA) for use as a food-contact polymer back in 1995 and published their results in Food and Chemical Toxicology.
They tested PLA under a variety of typical food storage conditions and measured what leached out into food-simulating solvents, such as Ethanol (what you find in liquor) and acetic acid (what you find in Vinegar). The storage conditions were varied with a bunch of short and long term storage conditions. They even heated the some samples to 60°C to simulate food serving conditions.
The study found that PLA is Generally Recognized As Safe (GRAS) when used in contact with food. Their summary concluded that PLA releases a small amount of lactic acid into foods. Lactic acid is a common food ingredient, that is even found in breast milk. They estimated that the amount of lactic acid people would consume from PLA to be about 700 times less than the lactic acid intake of breast-fed infants.
Ok, so while PLA is food safe, you need to keep a couple of other things in mind:
- Many 3D printer hot ends contain materials that are certainly not food safe. The only exception being the new all stainless steel model by Prusa. So if you are not using an all stainless steel hot end, trace amounts of nasties could find their way from your printer hot end, into your model and eventually into your food.
- Most PLA is coloured. So other additives have been added to your PLA to give it a funky colour. If you are printing things that contact foods, you should stick with ‘virgin’ or ‘natural’ PLA.
- It is going to be near impossible to keep your printed objects clean. 3D prints are covered with nooks and crannies like those that PomeroyB illustrates under their microscope. These little pores, when filled with food are a fertile breading ground for bacteria that could give you a nasty case of food poisoning. You should consider prints that come in contact with food as disposable, and throw them away after use.
Edits:
- 2021-06-04 - Removed broken Diamond Age link.
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