3D Prints and Food

We recently ran a post about a cute little 3D printed elephant that could dispense booze. The design didn’t actually have the plastic touching the liquid — there was a silicone tube carrying the shots. However, it did spark a conversation at the secret Hackaday bunker about how safe it is to use 3D printed objects for food. In particular, when I say 3D printing, I’m talking fused deposition modeling. Yes, there are other technologies, but most of us are printing using filament laid out in layers with a hot nozzle.

There’s a common idea that ABS is bad in general, but that PET and PLA are no problem because there are food-safe versions of those plastics available. However, the plastic is only a small part of the total food safety picture. Let me be clear: I am not a medical professional and although my computers have run a few plastics plants in years past, I am not really an expert on polymer chemistry, either. However, I don’t use 3D printed materials to hold or handle food and while you might not drop dead if you do, you might want to reconsider.

It is true that some plastics are not food safe. The US Food and Drug Administration (FDA) talks about “food contact substances” and has a lot of technical reading on the subject including this mostly readable introduction. There’s even a database with lots of materials (not just plastics) that are food safe.

However, even if some plastics can be food safe, that doesn’t mean that the $11 spool you bought on eBay is actually food safe. You don’t usually know who made it, how impure it is, or what’s been added to it for pigmentation or to modify other properties. However, let’s assume you locate food-grade filament from a trusted supplier. Is that the only problem? Turns out, it isn’t even the biggest problem.

Bacteria

Paradoxically, the biggest problem is microscopic. If you cook or store food much, you probably know that everything you eat is full of bacteria and other little critters. Leave some leftovers out tonight if you don’t believe that. If you make a cup using injection molding with a food-safe plastic, you shouldn’t have a problem as long as you wash the thing after each use. A 3D printed object, though, is going to have little cracks and spaces, especially where the layers make contacts. These are perfect places for germs to hide and multiply. Some foods, too, are worse than others. Raw eggs and meat, for example, are notorious for having dangerous bacterial growth.

There are two schools of thought here. If you are making something disposable, this might not be a big deal. Whatever bacteria get trapped wind up in the trash. The other thing people will do is use a food-safe sealant like polyurethane or silicone to cover the food contact surfaces. Of course, now you need to be sure the sealant is really food grade. In the case of the elephant, it wasn’t so much a sealant as just running a tube through the plastic.

There has been work on making antibacterial plastics. The video below shows one such plastic and it is even dishwasher safe.

Speaking of Cleaning

It isn’t fun to think about, but one reason dishes get clean in a dishwasher isn’t from the elbow grease, but from the hot water. Some of the best plastics for food — PLA, for example — may deform under dishwasher hot water. So even if you aren’t worried about hiding bugs, you still may not be able to get the plastic really clean. We haven’t tried it, but we hear the best practice is to use warm water and antibacterial soap.

Of course, the same thing happens if you print a PLA soup bowl and then fill it with hot soup. That would be a very bad idea. Not that you can’t find plastics with better temperature resistance, but remember things like ABS are full of nasty chemicals and are generally regarded by most people as not safe for food.

Oddly enough, though, the FDA actually lists conditions where ABS is food safe. Just like with PLA, though, there is no assurance your cheap spool of ABS meets those requirements. Note, too, that they disallow ABS coming into contact with alcohol.

Contamination

Well, you’ve found your food grade filament and you’ve perfected your process so you will wind up with a cleanable surface, but you still aren’t in the clear. Your filament is going to pass through an extruder and a hot end. Are any of those parts going to leave an unpleasant residue? Brass nozzles, for example, often contain lead. Your gear or hobbed bolt that bites into the filament to move it may have some bad things, too.

There is some thinking that an all-metal hot end is safer than the traditional PEEK/PTFE hot end. However, a lot of cheap “metal” hot ends have some plastic internal components. Again, you have to think of all the things that the plastic can touch. Probably would be a good idea if all those surfaces were cleanable, too.

Keep in mind, too, that your nozzle probably has remains from all the plastic you’ve printed with it before. So that implies you ought to have a machine just for food-safe printing. Well, at least the parts of the printer that touch the filament.

Studies show that 3D printing generates ultrafine particles. There isn’t a clear consensus about the health risks of breathing and ingesting these nanoparticles. You get the same thing from laser printers, but — honestly — you probably aren’t eating anything off a laser printed surface.

You can face a variation on this same problem if you print with food. For example, a printer that extrudes chocolate or icing shouldn’t allow the food to contact bad things on the way to the print. Cleaning the food path, in that case, is super critical. There are certified printers for food like the Chef Jet in the video below.

Is Food Safe Filament Available?

If you are not worried about all the other problems, you might be looking for food-safe filament. There are a few out there, including some PET filaments. However, you can be sure if the filament is really food grade, the vendor is going to say so. For instance, there’s a safe PLA made by KeyTech (and probably others). You’ll still want to get the material safety data sheet (MSDS) and make sure. But if the vendor isn’t saying anything about food safety, it is a good bet the filament is not recognized as food safe.

What about PLA? There’s a lot of street wisdom that it is safe. After all, it is made from corn. If you have PLA with no pigment or other additives and has been made in a way to minimize unsafe contaminants, maybe it is acceptable. There was a study in 1995 that tested PLA with things that ought to leach out chemicals like booze — we don’t know if they used an elephant or not — and other solvents found in edible materials. They did find a small amount of lactic acid can leach into the food, but it wasn’t a serious concern.

To Eat or Not to Eat?

Lead solder is dangerous too, but I use enough of that. However, I’m not motivated to print food-safe plastics. I think allowing other people to use my 3D printed bowls and cups would be even worse since they would not likely understand the risk. We’ve heard people say that a plastic knife or cookie cutter doesn’t contact the food long enough to be dangerous. I don’t buy that, but I am not an expert. If you must do the cookie cutters, you might try putting plastic wrap between the food and the cutter.

I know of people who follow the tradition of drinking a shot from a shot glass printed on a new 3D printer. Even though the science says you shouldn’t put alcohol in ABS, I haven’t known anyone to die from that practice. However, the body is a complex system and long-term and cumulative effects may be happening that I don’t know about.

I warned you I’m not a doctor or a chemist. I’m also not a lawyer, but I really think selling 3D printed food carriers would be a dangerous undertaking. Of course, you could clearly mark it, or there are US laws about permanently marking items “Not for Food Use,” so that might be a loophole.

In the end, only you can decide how to proceed. But at least be sure you are doing enough research about the plastic and your printing apparatus to minimize your risk. Have you consumed food from 3D prints? Would you? Or will you continue to do so? Share your opinion in the comments.

Oh, one more thing. We certainly are not eating the bacon filament.

 

55 thoughts on “3D Prints and Food

  1. I printed a coffee mug out of ABS. Brushed with acetone to seal the larger crevices, poured in some acetone and swirled vigorously until dried to turn the interior into a solid fused surface. I let it cure for a week to make sure the acetone was all gone.

    I tested it with hot and cold water with food dye. Fill with dyed water, dump out, and wipe with paper towel. No dye on the towel so I’m pretty confident the crevices are sealed. Cracks appear on the exterior from wear and tear, but a q-tip and some acetone fuses them shut again.

    ABS might be toxic, but I grew up with food and drinks in toxic BPA containers and am somehow not dead, and since there’s already tons of plastic in all food anyway, I feel like my coffee mug is the least of my worries.

    1. It’s fallacious to assume that not dying means you weren’t harmed, or that exposure to one amount of chemical means exposure to more is a non issue. You may well be right, but that logic is really bad.

    2. There was that ABS FDM SCUBA 2nd stage posted here a while ago and it wouldn’t hold back water even only at the pressure difference of inhalation required to activate the air valve without filling with water form the porosity until it was sealed with ABS/acetone paste.
      With porosity like that I think FDM might be a way to begin to transfer a computer model into the world for making an injection mold positive or negative (lost PLA?) but probably not a good idea to jump right from FDM to lunchroom for anything that is actyally food enough for humans or harmful microbes to enjoy as sustinence.

    3. That seems to me to be a good point about BPA – the worst plastics are touching your food already.

      I would never endorse it for someone else, or feed my kids from my printer. But personally, my morning coffee ritual uses 3x 3D-printed parts. A bean scoop of the right size. A grounds funnel of the right size. A water scoop of the right size (to get the right water level in my “moka pot”). I guess there’s a real mold/bacteria risk with the water scoop but I don’t care yet – the water is boiled, anyways. I find they really do increase the convenience.

      But I would never put real food on a print, it would never get clean….

      1. BPA is hardly “the worst plastic”. The issue with BPA is that it leaches an estrogen-like chemical ONLY when washed with very hot water. So don’t wash in your dishwasher. Acceptable? I don’t think so. But hardly “the worst plastics”.

        Reusing the bottles from bottled water is bad because they are not intended for long term use. They develop cracks which harbor bacteria from your backwash and whatever may be in the water you refill them with. So it isn’t the plastic itself that is bad for you.

        An FDM printed item has the equivalent of cracks built-in in the form of the surface roughness of the layers. Smoothing it would help.

    4. There are a lot of misunderstandings (and a lot of industry spin and popular/clickbait hysteria) in this area, and the author might have done a bit more homework.

      The current CFR requires approval of Food Contact Substances (including primary packaging – the material that contacts the stored food) for obvious reasons as you probably don’t want unpolymerized monomers, plasticizers or other materials migrating into food if they’re not proven safe. On the other side of the coin, there is a lot of completely daft “information” out there about how we shouldn’t have chemicals in our foods (including the notorious dihydrogen monoxide), or your organic food should never be packaged in anything other than bespoke and gluten free woven bamboo or some such nonsense. Foodies are a pretty special bunch and cognitive dissonance has always been the short road to their wallets.

      How do you sort all of this out?

      Think of the current post in terms of a risk model:

      The first and most likely hazard is that the silly things will leak and you’ll get burned/splashed by whatever’s in it.

      Second – microbial accumulation. If you can’t clean it…really clean it, you’re likely to have a bad time at some point in the future, usually involving time spent in the bathroom. This is why your food service items are either disposable or smooth.

      Third – “toxins”; real ones, not the ones you go to an expensive spa to get rid of. HAD’s world is full of knockoffs and cheap fabrication and the attendant problems in electronics, so there’s no reason to assume that the spools of filament that we use in our printers have any particularly clean provenance. It’s most likely that you’ve got shops simply converting stock resin pellets to filament (or turning the extruder’s chopper off in the first place so that the pellets are filament) but there’s no reliable certification (and few HAD readers have mass spectrometers in their basements).

      That said, recycled plastic resin is used in food packaging all the time, but there are some caveats in the U.S. (the resin pellets have to be washed etc.). If it ever becomes an issue, I’d personally avoid dodgy acrylonitrile and styrene (which includes the “S” in ABS copolymer) because the monomers are carcinogens and food-grade versions have to be proven to be completely polymerized. More panicky sorts have declared that you’ll be dead before you hit the floor if you’re in the same hemisphere with any variety of the stuff, but that’s nonsense. That clear cocktail cup you got last week that had the annoying habit of cracking when you squeezed it? Styrene (food grade).

      Fourth – long term substance migration. When you start storing your custom-hopped IPA in printed bottles for long periods you may have something to worry about – three minutes in a coffee cup or overnight in the fridge is something else entirely. Adding serious heat to the equation can increase diffusion and mobility but with the low exposure level the likelihood of you keeling over is pretty slim. That microwave pizza? The silvery disk you cooked it on is polyester printed with metal flakes that gets enormously hot in order to toast the crust…think about that one.)

      With all of that said, you’re unlikely to see mass-manufacture printed containers at all for an entirely different reason – economics.

      3D Printers are just too slow and too expensive to compete, even in making prototype molds or (sintered metal) injection molding dies. They get used a lot at the marketing level to check design features and it sort of ends there for the simple reason that a printer shouldn’t be used to make the same thing over and over again in competition with highly efficient mass-production. The few attempts I’ve seen are for small custom shops that have a whole wall of printers operating at once in order to produce a slow stream of containers – similar to the way they used to duplicated videocassettes. They don’t stay in business very long. The concept of 3D printed packaging gets kicked around once in a while but only by people who don’t understand the astounding scale of production necessary (often tens of thousands per hour or more) and the highly restrictive economics (pennies apiece or less).

      As far as BPA and regulation, BPA won’t cause you to drop dead – it’s been used in can linings and dental materials for decades – but it may (or may not) interfere with the sexual maturation of people (it’s caused problems in the animal models). The first website you’ll find with “facts” is sponsored by the US chemical industry that has a deep stake in this, and it’s still used here since getting food regulations passed is a target-rich environment for lobbyists. Other countries have banned it.

      Basic food safety regulations in the US has a similar trajectory in the 1800s if you’re interested in such things – Britain had its Pure Food Act in 1875 and Congress and its lobbyists stalled it until 1906 when the appalling practices exposed in “The Jungle” caused meat exports to be embargoed by Britain and Germany, which cause the meat industry lobbyists to do a quick 180 to get the export markets back.

    5. From the link in the article: “Acrylonitrile/butadiene/styrene copolymer identified in this section may be safely used as an article or component of articles intended for use with all foods, except those containing alcohol, under conditions of use E, F, and G described in table 2 of §176.170(c) of this chapter.”

      Conditions E, F, and G are: “Room temperature filled and stored (no thermal treatment in the container)”, “Refrigerated storage (no thermal treatment in the container)”, and “Frozen storage (no thermal treatment in the container)”.

      So using ABS to handle higher temperatures takes it out of the conditions where US federal regulators have deemed it food safe.

    6. I think about all the ABS Lego bricks I used to chew on when I was a little pup. That didn’t kill me. I even ate one once, back then, and I’m still OK. It was a blue 1/3 height 1×1 that I had inside an inflated balloon that I had up to my mouth. I let it deflate for a bit and the balloon launched the brick deep into the back of my mouth and before I knew it, it was swallowed. I never did that again and moved on to doing other strange things. :-)

  2. I hope to be finishing building my first printer soon. I would like to participate in the shotglass tradition. I’m not worried about the microbial problem because it would be a one time thing. I wouldn’t drink from it again. But… I don’t want to buy food-safe filament. I already bought one spool each of ABS and PLA. I bought them at MicroCenter so.. not a faceless Ebay import store but they don’t say anything about being food safe on the box.

    So… I am trying to decide… is it likely to make any difference to my health, near or distant future if I do this the one time?

    1. One shot out of a glass you made? I’m not not an expert but your risk is going to be near zero compared to some of the other tings we do in life. My personal experience of working in a food packaging plant for 19 years tells me that the food on a supermarket shelve is going to be safe as there are procedures that are followed and multiple inspections done (yes I know there are failures but they are few and far between) I also have a sibling and several friends that do the whole home grown organic food thing and they always seem surprised when I turn down some of their “healthy” foods, and get upset when I try and explain that I just do not trust food that comes from non-regulated sources.
      Do the things you want based on your own judgment but do not let the little risks stop you from doing something, you could get hit by a falling Chinese space station next month do you plan to hide in a cave?

    2. Potential Acute Health Effects:
      Hazardous in case of skin contact (irritant), of eye contact (irritant), of inhalation. Slightly hazardous in case of skin contact
      (permeator), of ingestion.
      Potential Chronic Health Effects:
      Slightly hazardous in case of skin contact (sensitizer). CARCINOGENIC EFFECTS: A4 (Not classifiable for human or
      animal.) by ACGIH. MUTAGENIC EFFECTS: Mutagenic for mammalian somatic cells. Mutagenic for bacteria and/or yeast.
      TERATOGENIC EFFECTS: Classified PROVEN for human. DEVELOPMENTAL TOXICITY: Classified Development toxin
      [PROVEN]. Classified Reproductive system/toxin/female, Reproductive system/toxin/male [POSSIBLE]. The substance is toxic
      to blood, the reproductive system, liver, upper respiratory tract, skin, central nervous system (CNS). Repeated or prolonged
      exposure to the substance can produce target organs damage.

      … and that’s just the alcohol.

  3. > What about PLA? There’s a lot of street wisdom that it is safe. After all, it is made from corn.
    ABS is made from dinos. So it should be safe as well according to that wisdom.

    Even if your filament is food safe, your printer isn’t. The bras nozzle adds a tiny amount of metal contamination. Everything else the material touches also contaminates it. There is also the color additions and stuff which have affect on it.

    A PET based filament is most likely you safest bet if you want to be reasonably food safe.

    At the plus side, the pressure and heat you add during the extrusion process sterilize your material. So it starts out germ free.

    1. I will admit to having a limited sample size, but I have yet to observe a bra with nozzles. ;-)

      But seriously, yes, I mention that. Brass nozzles, in particular, can contain lead. Not to mention residue from previous prints.

  4. Of course, you can anneal PLA. Annealled PLA can withstand a rinse in boiling water just fine, so a run in the dishwasher or warm water and soap is fine.

    If you’re making a straw or something like it, you can print in a single, fat spiral to ensure a good seal.

  5. I wouldn’t eat or drink out of 3D printed items for many of the reasons mentioned above, but we should clarify that some ABS products have been certified safe for children to play with for decades (i.e. – Lego). These frequently end up in their mouths.

  6. Al and I (the Wlliams brothers?) were the “spirited debate” at Hackaday HQ. The shot glass displayed with some nice aged grappa in the headline was printed for the occasion, and tested by running through the dishwasher.

    PET-G filament seems to hold up to a 70 C cycle in the Whirlpool just fine, and it’s my go-to filament for food safety (and mechanical construction). I gave the red shot glass a scrub and rinse downstairs in the kitchen before using it — I figure that should handle all of the loose nozzle residue, and what’s left shouldn’t come loose too easily.

    “Food safe” is a funny thing. As Al mentioned, the crevices provide an outsized surface area for bacteria. But people use plastic cutting boards (oh the crevices!) for salmonella (I mean factory-farm chicken) all the time, and they get sick very seldom b/c they wash with soap and hot water. It’s shocking how effective that is.

    My use cases — drinks, pre-cooked food — are so much less extreme that I don’t worry. I’m not putting bad bacteria on the plastic surface in the first place, so there’s none going to grow. And a hot hand wash should take care of the rest.

    My opinion: when people start looking for bacteria, they find them. Touchscreens, public toilets, phone handsets, airplane seats. I’m guessing that if you multiply badness of the bacteria by their quantity, 3D printed utensils don’t even show up on the scale.

    (Not a food safety expert. These are my opinions and in no way do they represent Hackaday’s. I like funny cheeses, “undercook” meat, eat raw eggs, and make my own yogurt and free-fermented Belgian-style beer, so you probably shouldn’t be taking microorganism advice from me anyway.)

      1. From that article:

        “Based on the results of the SPI study, the estimated dietary intake of BPA from can coatings is less than 0.00011 milligrams per kilogram body weight per day. This level is more than 450 times lower than the maximum acceptable or “reference” dose for BPA of 0.05 milligrams per kilogram body weight per day established by the U.S. Environmental Protection Agency.”

        “Stated another way, an average adult consumer would have to ingest more than 230 kilograms (or about 500 pounds) of canned food and beverages every day for an entire lifetime to exceed the safe level of BPA set by the U.S. Environmental Protection Agency.”

        I don’t know the name for this type of argument — where you put something small into human terms and it seems absurdly large — but this was a slam dunk.

        And I don’t know enough about the BPA thing, or the EPA’s guidelines, to comment further.

        1. Yeah I think what worries me more is that I depend on every can I have to have this coating intact. I have no idea how they insure that. I mean, what are the odds that every one of the billion cans out there is perfectly coated every time? Now, I don’t know the risk of drinking a coke from an uncoated can, either, so…

          1. You won’t ever drink a Coke from an imperfectly coated can, because the phosphoric acid will eat right through the aluminum and the can will fail.

            So drink your dilute phosphoric acid safe in the knowledge that there won’t be any aluminum dissolved in it.

    1. Did you see the Mythbusters one with all the toothbrushes in the bathroom? They found bacteria on all of them. They kept one toothbrush, dry, in the office for the whole term of the experiment.

      Then at the end they ruined the whole thing *by bringing the control into the test environment* in order to moisten it and scrub it on a petri dish of agar. Of course they got bacteria on it. They didn’t prove there was fecal bacteria in the office, just that bringing a dry toothbrush into a bacteria laden environment will contaminate it.

  7. I use plastic cutting boards as food safe material on the CNC. My popcorn machine chute is made from that material. I can dishwash the board and it’s cleaned up nicely. Now I’ve got to read that article…thanks.

    1. and now that i’ve read it, i would have to say, plastic and wood are evenly matched unless you’re an idiot and cross contaminate. If you cut meats on the board and then vegetables, you run risk no matter what you use.

    1. I see our nozzles listed as material type MS58, which as far as I can find is CuZn39Pb3, and thus contains lead.

      Information also listed this as the most common brass, and the best for milling. So I would expect it to be quite common in parts you encounter.

    2. Probably about 100% of the time if your test is sensitive enough. Elements aren’t usually found pure in nature you know. Many kinds of metals usually have at least a little lead mixed in already before they are ever pulled from the ground. We have processes to separate the different kinds giving us “pure” metals but there is no such thing as completely 100% pure.

  8. This is a great example of a really well written article full of half truths and “what if” scare tactics that the author can’t back up. “What if this?…What if that?” Almost every statement has some waffling verbage that is used as an out for the author.

    To your 3 main points:

    BACTERIA (microscopic crevices) – Do you throw out your cutting board each time your use it? No you don’t. You sanitize it. In the absence of hot water or a dishwasher, a weak bleach solution will work great if you are really all that worried. (Next time you’re at a bar, see how much the bartender does to “wash” a pint glass – it’s a dip in a sanitizing solution, and then two rinses) And it’s not just cutting boards, you don’t think there are microscopic crevices/scratches in your favorite coffee cup, plate, or knife that bacteria can grow in? There are. Nothing is as “smooth” as you think it is when you look at it under an electron microscope.

    CONTAMINATION(from hot end) Use an all metal (AL) hotend with stainless steel nozzle. Why wasn’t that mentioned? Didn’t fit in the narrative I assume.

    SAFETY(from the filament) – I bet that high quality PLA is way better in terms of safety then that $0.25 drinking glass from walmart via China. Who knows what’s in that. I would guess most of us take in some led that gets in our hands from soldering, and not being able to get every single atom off of our skin before eating that ham sandwich. So how safe something is, is really way beyond the scope of this article and the author.

    Would I switch all my cups and plates to 3d printed stuff for everyday use? No – that would be unpractical. But would I take a shot out of a 3d printed shot glass, or cutting out some cookies? Yea – not a big deal. If you’re really that worried about your safety, I recommend you never leave the house. ;)

    1. I have printed several cookie cutters in PLA.
      (my printer only prints PLA, but any kind from ‘high end’ down to “cheapest china choice (c)” ones )
      No problem using it.
      I print them in blue, this way, I can spot leftovers and clean them.
      A simple dish-soap and sponge cleaning on the same direction as the printing (to nicely clean the inter layer space) is safe enough for my use.
      Anyway, plastic households can be much worst than cookies that will then be cooked.

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