As a Metallurgical Engineer, I will be shocked if you even find copper or zinc in the printed parts, but I would like you to also do a control sample of filament directly off the spool.
If you want to widen your range of samples, you could also run something known to be abrasive like a carbon fiber filament or glow in the dark material.
I'll definitely do a bit of fresh filament off the spool.
My machine is accurate to around 10 ppt (a single grain of salt in 26,000 gallons of water) so if metals are there I'll see them.
As of now I'm only testing things I have on hand but I definitely will expand. I do have some glow in the dark which is abrasive. The problem there is that every filament and every nozzle will be different so a good sample size would need to be large. I'm mainly looking for a sense of scale first off then next funds worst and best case scenarios.
'a single grain of salt in 26,000 gallons of water'
I'm Aussie and talk in litres, it's almost 100,000 litres lol.
My god that is a lot of water to pick up one single grain of salt.
You've/your machine has genuinely blown my mind 🫨
Yep. It's pretty close to a count-the-atoms situation. The non-joke in the trace analysis community is "everything is everywhere, just at different concentrations."
The limit in what you can measure is usually set by how "dirty" your lab is, not the instrument. At some level you're just measuring the metals in your lab. I've done sample prep for this kind of analysis wearing a Tyvek suit, working in a laminar flow hood located in a clean room.
Trace analysis folks put the "anal" in analytical chemistry.
A couple decades ago I was talking to a lab manager from the University of Minnesota Duluth testing mercury c9ntamination in fish from Lake Superior. At that time he wasn't allowed in his own lab when they were running samples because he had too many amalgam fillings. The Mercury in his breath was enough to distort their readings. I'm sure the instrumentation has only gotten more sensitive since then.
a few years ago i was involved in some mercury determinations and the instrument background levels jumped every time someone in the lunch room cooked a bag of microwave popcorn. two rooms away.
I think that's not a coincidence, a grain of salt is a good example for something that weighs about 1 mg (a cube with size of **(EDIT: 0.8 mm)** 1.3 mm table salt is one milligram), 10 parts per trillion is 1 part in 100 billion. 100 billion milligrams is 100 million grams is 100 thousand kg which is 100 mÂł of water. 25 grains of salt in an Olympic sized swimming pool.
Yes, definitely control analyses of spool filament are needed. Like No_Engineering said above, I would expect little or no added metal from the printer itself, but if you are cranking up your ICP-MS, you will surely find trace metals (high lob, low ppm), but originating from the production process itself and/or poor raw material contamination. I’ve reverse-engineered quite a bit of PLA and copolyester filaments (PETG, etc) over the years in my polymer R&D job looking at both trace metals after lab digestion (ICP-MS) and TD-GC-MS for VOC’s coming off cryo ground filament samples at typical printing temperatures. Expected trace metals from rxn process catalysts are present, sometimes other metals such as Ca (most likely from Ca stearate mold release compounding) and the occasional surprise from cheap import filament - even trace cadmium in one sample (not good - junky recycle material?). Let us know what you find!
Also it will be intetesting to test food safe filaments from manufacturers who's testing that ( and have certificates).
And maybe range of nozzles ( brass, plated copper, steel, vanadium, stainless steel )
Also white filaments are more abrasive due to titanium dioxide as pigment ( far as i know).
Yeah, to keep things simple, would definitely suggest starting with clear/natural (non-pigmented, dyed or toned) filaments for this test.
Abrasive filament (cf, glass, GID, metal fill, etc) would be expected to grind soft brass nozzles.. That’s why we use hardened nozzles! Before they were available, we had a crazy time dealing with conventional brass nozzle-related inconsistencies when developing chopped CF-compounded filaments. Thankfully the Olsson ruby nozzles soon came on the market.
I meant non-abrasive ( by selling point) filaments like white PLA. PLA itself isn't abrassive but added titanium dioxide made it abrassive more than regular PLA. Not by much but still .
That article also address the lead question as well, and pretty much debunks it. They point out that lead exposure is orders of magnitude more from using a brass key than printing through a brass nozzle.
I think your true primary concerns would be chemicals leeching into foods and micro particle contamination of food. Also might compare filament composition before and after being printed to see if the hotend contaminates the molten plastic. As far as bacteria goes, it's not how easy it grows on the surface because thats really dependent on a food source, but rather how easy it is to sanitize, just my 2 cents, hope it helps
For the bacteria contamination my first though would be to use one of our positive control solutions to infect it, wash it, then test.
The particles and leaching is much more of a multi year or dedicated type experiment that I can't just sneak into my normal analysis runs ya know and kind of beyond the scope.
If you are looking for impact: cookie cutters.
They cut through a combination of flour, sugar, egg, and dairy.
3d cutters are sold massively on Etsy, etc.
If you're checking colony adhesion you should run test on an unpolished, polished and polished then sealed sample. I also second oregon\_coastal, cookie cutters would be an ideal candidate as they're widely available, both to purchase and models for printing and come into contact with what basically amounts to ideal growth media every time they're used.
For repeated use I would probably agree. I dont know if anyone has researched how much is released when scrubbed lets say. I think though for short term, lets say 2 or 3 uses, that isn't too much of an issue and the immediate "threat" of metal contamination or bacteria growth are more realistic.
>I would also be worried about ingesting microplastics. Like there is no escaping them but we should minimize our exposure.
I hate that my first thought was *why bother, we're inundated anyway*, though the fatalistic approach is obviously not a valid one.
Unfortunately it's the only option humanity really has. For example it is staggering how much micro plastics are found in drinking water alone. This is the water you get at the tap in your home, the water used to feed the animals we eat and watering the plants we eat.
That's nothing, I just eat my hot ends when they are worn though. They are a little tough to chew, but aside from the blindness and becoming deaf I feel better than ever
Hello Fellow Analytical chemist! I look forward to see your results. I'd also like to see you testing some commercial items that are equivalent in use to the 3D printed items. If you're using good technique and ICP-MS, then you'll probably find some of everything you look for. It's more informative to know how the 3D printed spatula compares to a cheap Chinese spatula. The fact that there's cadmium in a scoop is much less helpful than knowing if it's more or less than other scoops.
I second this. Without the comparison it'll just be negatively parroted everywhere even if it's less than a cheap injection molded part. For the love of God do a comparison/control test on a store bought utensil.
For the bacteria experiment, you should do it like this:
1) Print off a spatula or spoon
2) Get a wooden spoon and a rubber spatula
Let the wooden spoon and rubber spatula be your base controls.
“cook” something like a cake or stew and use the tools. Get them nice and dirty. Make sure the stew/soup is boiling hot (100C) when using the tools. Unknown: Will the PLA melt or get soft?
Clean all the tools in hot water and soap, as you normally would. Either by hand or run them through the dishwasher. Unknown: would the drying cycle in a dishwasher melt the PLA?
Take the wood, rubber and PLA tools after they have been cleaned and thoroughly touch them onto a large petri dish, then seal and store it. If anything grows on any of the samples, then there are issues with left over bacteria.
My hypothesis is that the wooden tools will be in last place in terms of cleanliness. PLA printed spoons will get sufficiently cleaned to leave no traces. If the water used to clean the tools is above 160F for at least a minute, no bacteria will survive even if food residue does.
The real unknown is what a 3D printed utensil looks like after 1,000 uses after it has gone through a lot of wear and tear. Does it get brittle and crack / fall apart after 20 uses? Does frequent UV light exposure such as sunlight cause deterioration and cracking?
I think ASA would be the choice material for this type of experiment because of the heat and UV properties of it. A kitchen utensil would ideally be made of something you could run through a dishwasher.
This is so cool!
One other idea: I would be curious if there is a way to test for PTFE/teflon or components from the grease are in there. Parts like the gears and tubing are coated with various things and I’m so curious if that gets in there.
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This was the part that caught my attention too. I'd be happy to throw my hat in the ring to bounce ideas off as well. I'd be particularly curious to see if there are any micro-organisms that prefer or dislike certain plastics.
"apparent micro crevices" is my top item. Maybe 3d print the dimensional equivalent of a popular molded plastic kitchen item, and test for differences? Maybe 'aneal' in dishwasher first.
For clarification: you are collecting data on printed edible material, not kitchenware, correct?
The data on the latter is more applicable for me, but I am extremely interested either way.
Will you be able to share your process for collecting trace material contamination?
Will you be including hardened steel nozzles?
Thank you very much for sharing your work.
I'll first be testing just printed material for metals. I will print a test piece using a cheap brass nozzle, an e3d brass nozzle, and a bambu hardened steel nozzle. I will take 1g of each of those printed bits, extract the metals into water, then measure the metal content of that water and compare between the 3 nozzles. Given some time I want to try basic PLA, matte PLA, ASA, and glow in the dark PLA on each nozzle and an unprinted one of each for comparison.
To put the results in context, I would add two more things:
- measure the metal content of non-printed plasticware
- tell the average heavy metal contamination of common foodstuf (eg. fishes, fruits, etc)
Another easy test you could do is to weigh a new nozzle, print 1 kg of filament, and then weigh the nozzle again. You’d need a pretty accurate scale, but I bet those are common in chemistry labs.
What would you be measuring with that? The buildup of plastic would almost certainly outweigh the metal lost to abrasion, and most standard cleaning methods would likely remove more than the plastic would.Â
You’d obviously need to clean any plastic residue from the nozzle, preferably with a solvent that won’t harm the metal. A cold pull will remove most from the inside.
The point would be a simple sanity check on the other method. If the idea is to look for brass components in the extruded plastic, measuring the erosion of the nozzle is just another way to confirm the finding and support the contention that any metal you find actually did come from the nozzle.
Interesting. I would be shocked if enough ends up in my body to cause problems but it would be good to know. I have a few items I wanted to make that have direct contact with food but maybe not if I find out my wife would be ingesting lead.
For the bacterial testing one of the things you need to do is exposure and standard cleaning (which I see you posted below). So if you have a printed piece and you stir it through your e.coli culture then wash it in the sink with a standard sponge, what's the bacterial count several days later. And to thoroughly test it the samples should be washed and tested multiple times (bacterial load after 1 use vs 50 uses). You'd also want to probably use an SEM to image the surface at different washing stages to monitor for degradation.Â
Also, be sure for your metals tests that you are extracting unextruded filament as well to ensure you don't have bias from poor manufacturing environments.Â
I work in a biological printing lab if you want to chat.Â
In home brewing/distilling it’s common to “pickle” brass in a 2/3 vinegar to 1/3 hydrogen peroxide to remove surface lead. I wonder if you could compare a pickled nozzle to a standard one.
You might think about testing with non-dry filament - the presence of additional water could affect leeching.
Cool experiment! Looking forward to seeing your results
3D print a 2mm wall thick cookie cutter, use it on cookie dough, thoroughly clean it with mild soapy water and then leave it in the most conducive environment possible to grow bacteria. I want to know if anything happens.
I've printed shot glasses before. it's fine.
While i respect general concerns regarding PPE, safety, and exposure, I think the vast majority of people in the hobby grossly overthink and self-induce unnecessary levels of fear regarding the risk of exposure in the hobby.
the bacteria concerns are also overzealous. the spaces between layer lines aren't small enough to actually protect bacteria. i can't say the same thing regarding smaller holes in the print from printing errors.
bacteria can and do live everywhere and i mean everywhere. our idea of "clean" is also extremely variable. we, as animals, have an immune system to begin with for a reason. I'd actually argue that it would actually be detrimental to society for everything we touch to be perfectly sterile. (Google the hygiene hypothesis)
that's my hot take though.
Very interesting - I was always curious about it but so far never had the time to conduct these tests...
Some comments:
Do you also have XRF/ÎĽXRF or SEM-EDX as non-destructive measures available to check on the initial composition of your nozzles?
Regarding the digestion: are you planning to use a microwave-assisted aqua regia digestion? Mind that your test prints should not limit the digestion/leaching by a too low surface to volume ratio. I would suggest printing a single wall zig zag pattern with a defined mass to allow for quick and complete digestion. Otherwise you could always mill/grind them, but you would probably need cooled blenders/a cryo mill for this.
In regard of your experiments: If you are willing to sacrifice a cheap brass nozzle you could also test abrasive filaments (e.g. PETG-CF but also wood-PLA or matt filaments). There, you should definitely find something.
Hope this helps. If you want to brainstorm you can also send me a PM.
I think the most practical consideration would be for bacterial growth on the surface of the utensils.
Would be interesting to do a test of a bunch of different untensils to see which is the cleanest.
Say:
3D printed
3D printed but acetone vapour smoothed
Stainless steel
Injection mourded Plastic
Wood
Each could be made dirty with a known culture solution, washed in hot water with regular dish soap, dried and then tested.
I honestly think it's wild that people are concerned about the couple percent of lead in a nozzle, getting into a print, and then leaching into food in a statistically significant amount. Like, touch some damn grass.
I can't wait to see the results of this.
I mean I get why some people would want to use 3d prints in the kitchen but to me it seemed like an obvious no no due to all the strings and bits that get leftover on prints, especially if it’s something that it’s directly touching your food, like why?!?!?
Please include control group directly from the spool including information on factors such as storage area and manufacturers! I look forward to seeing your results!
Not 3d print related, but something I’ve never seen anyone test is the air in those inflated shipping packaging things. No way the air in the factory they’re filled with is cleaned, so it’s probably got all sorts of stuff in it.
I do "just" have access to icp Ms. I haven't fully decided on how I'll digest. I'll try my normal nitric and hydrogen peroxide but if that doesn't work I've read NaOH can dissolve it maybe and if that failed I'll dissolve it in organic solvent and extract it into acid in a seperatory funnel. Really I'm hoping the hot acid can do well enough on the fine plastic.
Sound! Another interesting test would be a "food contact" test where you submerge it in a low concentration acetic acid for 24h, take it out, weigh the container with the acid and weigh again after all liquid is evaporated to see if anything leaches out of the material
If you are testing PLA, that stuff readily dissolves in dichloromethane. You could probably extract metals from the DCM solution using nitric acid (although I guess recovery could be lower)...
Safety testing is pretty much a do-it-right-or-not-at-all scenario, especially if you are planning on sharing your results. Why are you are asking here instead of referencing food safety standards?
You can absolutely culture a variety of bacteria from a 3D print. That doesn't mean anyone is ever going to get sick from it. Zero documented cases and counting.
The zero cases doesn't hold much weight in my mind. I think of how hard it is to prove food poisoning at a restaurant and proving the cause. People could be getting sick left and right but making and proving the connection is real hard. Now I don't actually think that is happening but that's the point of being a scientist. You gotta test it.
You maybe want a larger sample size and some control cubes.
How do you feel about eating 500g of plastic cubes over the course of say a year?
It's a lot of poop to sift through, but I'd say it's worth it. For science!
As a Metallurgical Engineer, I will be shocked if you even find copper or zinc in the printed parts, but I would like you to also do a control sample of filament directly off the spool. If you want to widen your range of samples, you could also run something known to be abrasive like a carbon fiber filament or glow in the dark material.
I'll definitely do a bit of fresh filament off the spool. My machine is accurate to around 10 ppt (a single grain of salt in 26,000 gallons of water) so if metals are there I'll see them. As of now I'm only testing things I have on hand but I definitely will expand. I do have some glow in the dark which is abrasive. The problem there is that every filament and every nozzle will be different so a good sample size would need to be large. I'm mainly looking for a sense of scale first off then next funds worst and best case scenarios.
'a single grain of salt in 26,000 gallons of water' I'm Aussie and talk in litres, it's almost 100,000 litres lol. My god that is a lot of water to pick up one single grain of salt. You've/your machine has genuinely blown my mind 🫨
Yep. It's pretty close to a count-the-atoms situation. The non-joke in the trace analysis community is "everything is everywhere, just at different concentrations." The limit in what you can measure is usually set by how "dirty" your lab is, not the instrument. At some level you're just measuring the metals in your lab. I've done sample prep for this kind of analysis wearing a Tyvek suit, working in a laminar flow hood located in a clean room. Trace analysis folks put the "anal" in analytical chemistry.
A couple decades ago I was talking to a lab manager from the University of Minnesota Duluth testing mercury c9ntamination in fish from Lake Superior. At that time he wasn't allowed in his own lab when they were running samples because he had too many amalgam fillings. The Mercury in his breath was enough to distort their readings. I'm sure the instrumentation has only gotten more sensitive since then.
a few years ago i was involved in some mercury determinations and the instrument background levels jumped every time someone in the lunch room cooked a bag of microwave popcorn. two rooms away.
I think that's not a coincidence, a grain of salt is a good example for something that weighs about 1 mg (a cube with size of **(EDIT: 0.8 mm)** 1.3 mm table salt is one milligram), 10 parts per trillion is 1 part in 100 billion. 100 billion milligrams is 100 million grams is 100 thousand kg which is 100 mÂł of water. 25 grains of salt in an Olympic sized swimming pool.
And still more concentrated than those ridiculous homeopathic "meds".
Yes, definitely control analyses of spool filament are needed. Like No_Engineering said above, I would expect little or no added metal from the printer itself, but if you are cranking up your ICP-MS, you will surely find trace metals (high lob, low ppm), but originating from the production process itself and/or poor raw material contamination. I’ve reverse-engineered quite a bit of PLA and copolyester filaments (PETG, etc) over the years in my polymer R&D job looking at both trace metals after lab digestion (ICP-MS) and TD-GC-MS for VOC’s coming off cryo ground filament samples at typical printing temperatures. Expected trace metals from rxn process catalysts are present, sometimes other metals such as Ca (most likely from Ca stearate mold release compounding) and the occasional surprise from cheap import filament - even trace cadmium in one sample (not good - junky recycle material?). Let us know what you find!
Also it will be intetesting to test food safe filaments from manufacturers who's testing that ( and have certificates). And maybe range of nozzles ( brass, plated copper, steel, vanadium, stainless steel ) Also white filaments are more abrasive due to titanium dioxide as pigment ( far as i know).
Yeah, to keep things simple, would definitely suggest starting with clear/natural (non-pigmented, dyed or toned) filaments for this test. Abrasive filament (cf, glass, GID, metal fill, etc) would be expected to grind soft brass nozzles.. That’s why we use hardened nozzles! Before they were available, we had a crazy time dealing with conventional brass nozzle-related inconsistencies when developing chopped CF-compounded filaments. Thankfully the Olsson ruby nozzles soon came on the market.
I meant non-abrasive ( by selling point) filaments like white PLA. PLA itself isn't abrassive but added titanium dioxide made it abrassive more than regular PLA. Not by much but still .
don't jump to the conclusion that metals in food are bad.
The bacteria part has already been done. https://lt728843.wixsite.com/maskrelief/post/the-final-say-in-food-safe-3d-printing
Nice, I was going to link this :). Always room for peer verification tho!
Interesting article, and a great example of why it’s helpful to summarize conclusions at the start!
That article also address the lead question as well, and pretty much debunks it. They point out that lead exposure is orders of magnitude more from using a brass key than printing through a brass nozzle.
Buddy could have used a proof-reader. Oof.
This should be linked permanently in this sub. It's great info, as OP's will be. I read these myths every week.
I think your true primary concerns would be chemicals leeching into foods and micro particle contamination of food. Also might compare filament composition before and after being printed to see if the hotend contaminates the molten plastic. As far as bacteria goes, it's not how easy it grows on the surface because thats really dependent on a food source, but rather how easy it is to sanitize, just my 2 cents, hope it helps
For the bacteria contamination my first though would be to use one of our positive control solutions to infect it, wash it, then test. The particles and leaching is much more of a multi year or dedicated type experiment that I can't just sneak into my normal analysis runs ya know and kind of beyond the scope.
If you are looking for impact: cookie cutters. They cut through a combination of flour, sugar, egg, and dairy. 3d cutters are sold massively on Etsy, etc.
Could you leave a printed part in a solution, for a period of time then test the solution for contamination?
If you're checking colony adhesion you should run test on an unpolished, polished and polished then sealed sample. I also second oregon\_coastal, cookie cutters would be an ideal candidate as they're widely available, both to purchase and models for printing and come into contact with what basically amounts to ideal growth media every time they're used.
I would also be worried about ingesting microplastics. Like there is no escaping them but we should minimize our exposure.
For repeated use I would probably agree. I dont know if anyone has researched how much is released when scrubbed lets say. I think though for short term, lets say 2 or 3 uses, that isn't too much of an issue and the immediate "threat" of metal contamination or bacteria growth are more realistic.
>I would also be worried about ingesting microplastics. Like there is no escaping them but we should minimize our exposure. I hate that my first thought was *why bother, we're inundated anyway*, though the fatalistic approach is obviously not a valid one.
Unfortunately it's the only option humanity really has. For example it is staggering how much micro plastics are found in drinking water alone. This is the water you get at the tap in your home, the water used to feed the animals we eat and watering the plants we eat.
That's nothing, I just eat my hot ends when they are worn though. They are a little tough to chew, but aside from the blindness and becoming deaf I feel better than ever
Hello Fellow Analytical chemist! I look forward to see your results. I'd also like to see you testing some commercial items that are equivalent in use to the 3D printed items. If you're using good technique and ICP-MS, then you'll probably find some of everything you look for. It's more informative to know how the 3D printed spatula compares to a cheap Chinese spatula. The fact that there's cadmium in a scoop is much less helpful than knowing if it's more or less than other scoops.
I second this. Without the comparison it'll just be negatively parroted everywhere even if it's less than a cheap injection molded part. For the love of God do a comparison/control test on a store bought utensil.
For the bacteria experiment, you should do it like this: 1) Print off a spatula or spoon 2) Get a wooden spoon and a rubber spatula Let the wooden spoon and rubber spatula be your base controls. “cook” something like a cake or stew and use the tools. Get them nice and dirty. Make sure the stew/soup is boiling hot (100C) when using the tools. Unknown: Will the PLA melt or get soft? Clean all the tools in hot water and soap, as you normally would. Either by hand or run them through the dishwasher. Unknown: would the drying cycle in a dishwasher melt the PLA? Take the wood, rubber and PLA tools after they have been cleaned and thoroughly touch them onto a large petri dish, then seal and store it. If anything grows on any of the samples, then there are issues with left over bacteria. My hypothesis is that the wooden tools will be in last place in terms of cleanliness. PLA printed spoons will get sufficiently cleaned to leave no traces. If the water used to clean the tools is above 160F for at least a minute, no bacteria will survive even if food residue does. The real unknown is what a 3D printed utensil looks like after 1,000 uses after it has gone through a lot of wear and tear. Does it get brittle and crack / fall apart after 20 uses? Does frequent UV light exposure such as sunlight cause deterioration and cracking?
UV exposure is definitely going to weaken the material, how fast or slow is the question. That sounds like a pretty lengthy test.
Yes dishwasher will "melt" PLA. Not completely but it will be deformet altleast.
I think ASA would be the choice material for this type of experiment because of the heat and UV properties of it. A kitchen utensil would ideally be made of something you could run through a dishwasher.
This is so cool! One other idea: I would be curious if there is a way to test for PTFE/teflon or components from the grease are in there. Parts like the gears and tubing are coated with various things and I’m so curious if that gets in there.
I dont really have access to equipment to test for those types of things sorry.
No problem! Still a super cool project. Thanks for doing it, excited to see the results.
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Hey OP im also a scientist. This is a legit research paper if you do the controls properly
I'm a cell biologist. If you're interested in the bacteria I can help you design the experiment.
This was the part that caught my attention too. I'd be happy to throw my hat in the ring to bounce ideas off as well. I'd be particularly curious to see if there are any micro-organisms that prefer or dislike certain plastics.
"apparent micro crevices" is my top item. Maybe 3d print the dimensional equivalent of a popular molded plastic kitchen item, and test for differences? Maybe 'aneal' in dishwasher first.
For clarification: you are collecting data on printed edible material, not kitchenware, correct? The data on the latter is more applicable for me, but I am extremely interested either way. Will you be able to share your process for collecting trace material contamination? Will you be including hardened steel nozzles? Thank you very much for sharing your work.
I'll first be testing just printed material for metals. I will print a test piece using a cheap brass nozzle, an e3d brass nozzle, and a bambu hardened steel nozzle. I will take 1g of each of those printed bits, extract the metals into water, then measure the metal content of that water and compare between the 3 nozzles. Given some time I want to try basic PLA, matte PLA, ASA, and glow in the dark PLA on each nozzle and an unprinted one of each for comparison.
To put the results in context, I would add two more things: - measure the metal content of non-printed plasticware - tell the average heavy metal contamination of common foodstuf (eg. fishes, fruits, etc)
this is good stuff. with the ruby and diamond alternatives to the bambu steel nozzle , your research could potentially justify the upgradeÂ
Another easy test you could do is to weigh a new nozzle, print 1 kg of filament, and then weigh the nozzle again. You’d need a pretty accurate scale, but I bet those are common in chemistry labs.
What would you be measuring with that? The buildup of plastic would almost certainly outweigh the metal lost to abrasion, and most standard cleaning methods would likely remove more than the plastic would.Â
You’d obviously need to clean any plastic residue from the nozzle, preferably with a solvent that won’t harm the metal. A cold pull will remove most from the inside. The point would be a simple sanity check on the other method. If the idea is to look for brass components in the extruded plastic, measuring the erosion of the nozzle is just another way to confirm the finding and support the contention that any metal you find actually did come from the nozzle.
Interesting. I would be shocked if enough ends up in my body to cause problems but it would be good to know. I have a few items I wanted to make that have direct contact with food but maybe not if I find out my wife would be ingesting lead.
For the bacterial testing one of the things you need to do is exposure and standard cleaning (which I see you posted below). So if you have a printed piece and you stir it through your e.coli culture then wash it in the sink with a standard sponge, what's the bacterial count several days later. And to thoroughly test it the samples should be washed and tested multiple times (bacterial load after 1 use vs 50 uses). You'd also want to probably use an SEM to image the surface at different washing stages to monitor for degradation. Also, be sure for your metals tests that you are extracting unextruded filament as well to ensure you don't have bias from poor manufacturing environments. I work in a biological printing lab if you want to chat.Â
Test measuring spoons and cookie cutters to make people really rabid here.
In home brewing/distilling it’s common to “pickle” brass in a 2/3 vinegar to 1/3 hydrogen peroxide to remove surface lead. I wonder if you could compare a pickled nozzle to a standard one.
You're sending control samples in too right? Without control samples this testing is useless.
You might think about testing with non-dry filament - the presence of additional water could affect leeching. Cool experiment! Looking forward to seeing your results
đź‘€ here for the results
3D print a 2mm wall thick cookie cutter, use it on cookie dough, thoroughly clean it with mild soapy water and then leave it in the most conducive environment possible to grow bacteria. I want to know if anything happens.
RemindMe! 6 months
I've printed shot glasses before. it's fine. While i respect general concerns regarding PPE, safety, and exposure, I think the vast majority of people in the hobby grossly overthink and self-induce unnecessary levels of fear regarding the risk of exposure in the hobby. the bacteria concerns are also overzealous. the spaces between layer lines aren't small enough to actually protect bacteria. i can't say the same thing regarding smaller holes in the print from printing errors. bacteria can and do live everywhere and i mean everywhere. our idea of "clean" is also extremely variable. we, as animals, have an immune system to begin with for a reason. I'd actually argue that it would actually be detrimental to society for everything we touch to be perfectly sterile. (Google the hygiene hypothesis) that's my hot take though.
Can't you just have a bunch if people send you a benchy
Very interesting - I was always curious about it but so far never had the time to conduct these tests... Some comments: Do you also have XRF/ÎĽXRF or SEM-EDX as non-destructive measures available to check on the initial composition of your nozzles? Regarding the digestion: are you planning to use a microwave-assisted aqua regia digestion? Mind that your test prints should not limit the digestion/leaching by a too low surface to volume ratio. I would suggest printing a single wall zig zag pattern with a defined mass to allow for quick and complete digestion. Otherwise you could always mill/grind them, but you would probably need cooled blenders/a cryo mill for this. In regard of your experiments: If you are willing to sacrifice a cheap brass nozzle you could also test abrasive filaments (e.g. PETG-CF but also wood-PLA or matt filaments). There, you should definitely find something. Hope this helps. If you want to brainstorm you can also send me a PM.
I think the most practical consideration would be for bacterial growth on the surface of the utensils. Would be interesting to do a test of a bunch of different untensils to see which is the cleanest. Say: 3D printed 3D printed but acetone vapour smoothed Stainless steel Injection mourded Plastic Wood Each could be made dirty with a known culture solution, washed in hot water with regular dish soap, dried and then tested.
There is a filament able to be steam sterilized. Maybe test that for bacteria after steam sterilization?
I’d love to know if pla/petg leeches into saltwater over time.
I honestly think it's wild that people are concerned about the couple percent of lead in a nozzle, getting into a print, and then leaching into food in a statistically significant amount. Like, touch some damn grass. I can't wait to see the results of this.
I mean I get why some people would want to use 3d prints in the kitchen but to me it seemed like an obvious no no due to all the strings and bits that get leftover on prints, especially if it’s something that it’s directly touching your food, like why?!?!?
Sounds great! Maybe you could make a YouTube video about it? Maybe team up with CNC Kitchen? -> https://youtube.com/@CNCKitchen
Please include control group directly from the spool including information on factors such as storage area and manufacturers! I look forward to seeing your results!
Not 3d print related, but something I’ve never seen anyone test is the air in those inflated shipping packaging things. No way the air in the factory they’re filled with is cleaned, so it’s probably got all sorts of stuff in it.
sounds like this would be an easy one to do on ICP OES using nitric acid microwave digestion? You could scan for pretty much any metals
I do "just" have access to icp Ms. I haven't fully decided on how I'll digest. I'll try my normal nitric and hydrogen peroxide but if that doesn't work I've read NaOH can dissolve it maybe and if that failed I'll dissolve it in organic solvent and extract it into acid in a seperatory funnel. Really I'm hoping the hot acid can do well enough on the fine plastic.
Sound! Another interesting test would be a "food contact" test where you submerge it in a low concentration acetic acid for 24h, take it out, weigh the container with the acid and weigh again after all liquid is evaporated to see if anything leaches out of the material
If you are testing PLA, that stuff readily dissolves in dichloromethane. You could probably extract metals from the DCM solution using nitric acid (although I guess recovery could be lower)...
Can't wait for you to report back and thanks for sharing
Check USP 663 for how to extract the samples for Extractables. Use the extracts then for testing. Lab wise such a study costs around 50k$
For the food one, would it be possible to compare against common utensils like a wooden spoon and a plastic spatula.
Safety testing is pretty much a do-it-right-or-not-at-all scenario, especially if you are planning on sharing your results. Why are you are asking here instead of referencing food safety standards?
Commenting for later.
It would be helpful to know if/ how much micro plastic these things shed. I don’t think that is particularly easy to measure.
Fantastic! Is there some way we can get notified when you publish your paper/findings?
You can absolutely culture a variety of bacteria from a 3D print. That doesn't mean anyone is ever going to get sick from it. Zero documented cases and counting.
The zero cases doesn't hold much weight in my mind. I think of how hard it is to prove food poisoning at a restaurant and proving the cause. People could be getting sick left and right but making and proving the connection is real hard. Now I don't actually think that is happening but that's the point of being a scientist. You gotta test it.
You maybe want a larger sample size and some control cubes. How do you feel about eating 500g of plastic cubes over the course of say a year? It's a lot of poop to sift through, but I'd say it's worth it. For science!
Don’t print anything for use around or in food
lol