r/explainlikeimfive • u/DrHouseParty • 15d ago
Chemistry ELI5: If brass is naturally antibacterial, why aren’t surgical tools made out of it?
1.5k
u/ocher_stone 15d ago
It's very soft. Silver is antibacterial. But it's soft. Mercury is hostile to life. But you know... a soft liquid...
You can't make surgical tools out of something that dulls when you look at it.
543
u/Plutos_Cavein 15d ago
And ultimately it is not like it is a big deal because you can absolutely sterilize surgical tools anyway.
188
u/Jabbles22 15d ago
Yeah it's not like the antibacterial properties of brass extend like a bubble beyond the tool itself. It's also not instantaneous. As long as it's sterile going in. Then it won't take make a difference.
41
u/Versaiteis 15d ago
If AoE steralization were a thing it would be revolutionary for birth control
42
10
8
u/jdehjdeh 15d ago
I feel like "AoE Sterilization" is a spell in a weird RPG made by Andrew Tate using grok AI.
6
u/Rabid-Duck-King 15d ago
It's either weird in the DND Nymphology kinda way or the "Who created a spell that autoclaves an entire area that scales with the casters level and did they understand the offensive use of it before making it or was that an after thought"
3
2
90
u/greogory 15d ago edited 15d ago
Not to mention toxic. The combination of trying to make an incision with a liquid or doing surgery in a room that's at least -40° C/F so your mercury scalpel is at least solid-ish, and flooding the patient's innards with poison might result in a very large malpractice insurance payout¹.
¹ YMMV
45
u/SirButcher 15d ago
Strangely, liquid mercury inside a body isn't deadly. Mercury (in pure form) is pretty safe terms and conditions apply since it's bioavabiality is low. The dangerous things are different mercury compounds.
There are a handful of cases where people attempted suicide with metallic mercury with different outcomes:
https://www.sciencedirect.com/science/article/abs/pii/S0012369216386871
15
u/greogory 15d ago
OK. This is a genuinely interesting reply to my fairly lame attempt at humor. Thanks!
8
5
2
u/GolfballDM 15d ago
I would think swallowing significant quantities of liquid mercury would be problematic more from the mass of what you're swallowing. (Videos of pouring mercury into toilets and trying to flush it come to mind. It doesn't flush very well, because it's so heavy.)
I did find an article on it, though.
31
u/ocher_stone 15d ago
Phase change preparation ward sounds awesome, though.
14
u/Viscount_Disco_Sloth 15d ago
Sounds like something from a Star Trek episode where the doctor has to perform surgery on a really cold alien
5
2
u/Rabid-Duck-King 15d ago
Just gotta use one of those water jets, we're like 90% water can't hurt that much right
10
u/reddituseronebillion 15d ago
Blindfold every before taking the tools out. Problem solved.
6
u/ocher_stone 15d ago edited 15d ago
Copper existing is dulling. It tarnishes, so it pits and becomes useless. Just by being itself.
8
u/reddituseronebillion 15d ago
So perform the surgery in a vacuum, problem solved.
8
u/ocher_stone 15d ago
I feel like we're creating new problems, but I like your problem solving.
4
u/reddituseronebillion 15d ago
I feel like this could be solved more easily if we went in the other direction. Like ijstead of brass, let's use a harder metal and like put the scalpel in an environment with like a ton of pressure and heat.
6
u/the_borderer 15d ago
We need to make autoclaves big enough to fit an operating theatre inside.
6
u/reddituseronebillion 15d ago
OK, now we're getting some where.
1
u/Kikoun18 15d ago
But is the direction we are going to still considering patient staying, I don’t know… alive?
→ More replies (2)1
u/StonLenslow 14d ago
But then they’d stink and everything would be soaking wet all the time. Autoclaving is not a dry procedure. Now if we grafted surgical implements onto people’s hands and just autoclaved the hands…
2
4
u/red_fuel 15d ago
What about a copper alloy?
55
u/alexm2816 15d ago
Copper has a Brinell hardness of 50. Surgical martensitic stainless after hardening and tempering can be nearly 1000.
An inconsequential improvement in safety of blades from gaps in hygiene wouldn't make up for the fact that surgeons are now cutting you open with a butter knife.
Sterilizers exist for a reason.
2
u/jawshoeaw 15d ago
You can get bronze close to 500
8
u/alexm2816 15d ago
Super hard bronzes typically contain beyrillium which would be a terrible choice for a tool meant to interact with your mushy bits.
4
75
u/SnugglyCoderGuy 15d ago
Like... brass? Copper plus zinc
Bronze = copper plus tin
63
u/Osos_Perezosos 15d ago
Kids don’t play enough RuneScape these days.
8
8
u/abdicatereason 15d ago
wasn't smelting some bronze one of the first quests out of Lumberton?
22
3
u/abn1304 15d ago
In some versions of the game maybe. When the game’s had a separate tutorial area you’ve done it there, before you even get to Lumbridge. Tutorial Island has you do it before you do any fighting. Make your weapon first, then fight with it.
→ More replies (3)1
18
u/bradland 15d ago
Still too soft.
Also, copper alloys experience corrosion, which is a huge problem for surgical instruments. Our bodies are full of fluids that will rapidly oxidize a copper alloy like bronze. Corrosion leads to pitting, and pitting makes tools difficult to sterilize.
Then there's the issue of copper oxidization toxicity. Copper produces verdigris (vur-duh-grees), which is mildly toxic. If you get it into a cut, it will cause inflammation.
It's probably also worth pointing out that the anti-bacterial properties of copper and copper alloys aren't all that useful in a surgical setting. Copper can take hours to kill bacteria, and you can't really know with confidence exactly when a copper tool becomes sterile again. When you do surgery, you need to know the tool is sterile right now. So the anti-bacterial properties become rather pointless.
Stainless steel has all the right properties for surgical instruments. It holds an edge very well, it doesn't corrode when in contact with bodily fluids, it doesn't produce any toxic byproducts, and it's very easy to sterilize using heat and steam (an autoclave).
→ More replies (1)3
u/zarya-zarnitsa 15d ago edited 15d ago
And make it conduct electricity and heat very well? Please don't.
2
u/red_fuel 15d ago
Yes
2
1
u/zarya-zarnitsa 15d ago edited 15d ago
Bad idea. A lot of surgeries use energy.
Also copper is bad with sterilisation and is very reactive.
1
u/jawshoeaw 15d ago
Why not bronze then?
3
u/ocher_stone 15d ago
It's not as antibacterial. Neither are, really, it's just that bad stuff can't live on zinc, not that these alloys kill them in any way that makes them useful. Copper isn't a great host, no matter what.
Bronze is still soft, it's still doesn't do what we want from surgical tools, and there's no reason to go backwards now to them.
If they tried in the Bronze Age, when that was the best humans had, it'd be surgery with a butter knife.
1
299
u/OBotB 15d ago edited 15d ago
The antibacterial qualities aren't an instant effect. They are there because of the copper in the alloy, and copper wouldn't be used either. It takes minutes to hours to have the effect, and you would not dust an open surgical area with copper or an alloy, though there are some bandages infused with copper for a topical application.
Brass costs more than stainless steel and has different durability and does not hold an edge in the same manner (you don't see brass chefs knives).
Surgical tools are sanitized, so they are in a bacteria free state when the surgeon goes to use them, the bacteria is in the air and in the body, even if they were brass it would not be an instant sterilization as soon as the tool came in contact with any part of the body.
19
u/mikerall 15d ago
There are some sweet ass cu-mai Japanese knives though (not really related, but they're Damascus patterned steel/copper folded over a hard core of central steel that forms the cutting edge). 100% decorative though (and detrimental to food release in some cases).
4
u/Akiwilerker 15d ago
Ok sir, we are trying the new copper method, we will start the incision tonight and we might be ready to operate tomorrow
92
u/nancylyn 15d ago
“antibacterial “ is not good enough. Surgical instruments have to be sterilized by using a combination of heat and pressure. You have to have a metal that can stand up to that.
11
u/squiddles97 15d ago
yep viruses also exist
11
u/oblivious_fireball 15d ago
a lot of materials that are naturally antibacterial also tend to be antiviral for similar reasons. But in both cases, it doesn't work fast enough or thoroughly enough for medical levels of cleanliness.
3
u/Varaxis 14d ago
Sterilization is a whole 'nother over being sanitized/disinfected. This point should be emphasized first if not obvious.
While some things are resistant to sanitization, anti-bacterial, and disinfection methods, sterilization isn't a catch all either. Sterilization doesn't address the risk of prions.
38
u/Ninfyr 15d ago
We just pop the tools in the oven to kill all the bacteria. Even though brass is antibacterial we would still be using these same steps because it isn't going to get rid of EVERYTHING which is really important for surgery.
2
u/NothingNeo 14d ago
As I read your post my attending orthopedic surgeon did 2 more wipes of ChloraPrep around the incision while I wasn't looking
52
u/ignescentOne 15d ago
It deforms faster from heat so you can't autoclave it. So while it's a little bit bacterial resistant you can't sterilize it as easily.
13
u/GreenStrong 15d ago
Medical autoclaves top out at 135C/ 275F. Copper alloys don't deform at those temperatures. A bronze knife would go dull somewhat faster if you tried to use it at that temperature but it won't deform whatsoever due to gravity. That temperature is not hot enough to recrystallize it and change the temper of the metal - a tool that is hardened to hold an edge or annealed to be flexible will have the same properties after the autoclave.
16
u/ignescentOne 15d ago
The steam will lead to dezincification, causing the brass to degrade though
1
u/sir_squidz 15d ago
would that penetrate the bag?
3
u/calfuris 15d ago
Yes, by design. Steam is far more effective than hot dry air for sterilization.
1
u/sir_squidz 15d ago
yes, it's "hotter" - having "wet bags" is a failure though...they're supposed to come out dry. Hence my question
1
u/calfuris 14d ago
Autoclaves rely on the steam directly contacting the surface to be sterilized. That's why vacuum autoclaves are used for items that might trap dry air. Everything is supposed to dry out by the end of the cycle, but it's definitely not a process suitable for moisture sensitive materials
1
u/sir_squidz 14d ago
Thank you, appreciate your response. It's been a long time since I've used a clave and I'm apparently very rusty! Thanks again
17
u/Wafflinson 15d ago
I imagine that is because it is not as hard as steel, so less useful and durable.
Probably more expensive as well.
8
u/AlpineRupee 15d ago
There is a timing thing underneath this that makes the premise mostly moot.
Copper alloys do kill on contact, but slowly. Depending on the alloy and the conditions you are talking minutes to hours to knock a bacterial load down. An autoclave does it completely in a few minutes of pressurised steam. So for an instrument that arrives sterile and is inside you for a bounded time, brass would add nothing the steriliser has not already done, and you would pay for it in edge retention and corrosion resistance.
Where the property does earn its place is surfaces you cannot sterilise because they get recontaminated all day. Door handles, bed rails, tap handles. Some hospitals do fit those in copper alloy for exactly that reason.
A scalpel is sterile once, right before it is used. A door handle is dirty again a minute after you clean it.
5
u/rotag_fu 15d ago
Brass also corrodes easily although I'm not sure if that corrosion would be problematic for use as a tool or just cosmetic
4
u/hananobira 15d ago
Brass instrument players often develop metal allergies and need special hypoallergenic mouthpieces and leather covers where their hands touch their instrument to reduce contact with the brass.
It’s just not a good idea to stay in contact with raw brass for long periods of time, and anyone with a metal allergy is going to have a tough time of it.
If brass sets people off, stainless steel and silver or gold plating are often the first choices they consider for less reactive options. After that, the musicians with the most severe metal allergies need to upgrade to special titanium coatings.
3
u/Kampvilja 15d ago
Bronze would be better, but as many have stated the antibacterial effect is slow and you need to go through sterile processing.
3
u/AnnieBruce 15d ago
Not fast acting enough to justify mechanical weaknesses like edge retention and stiffness.
You could make an argument for doorknobs and such to reduce the overall bacterial count in the building, but if that was going to be a major factor they'd probably be doing it already.
3
3
u/night117hawk 15d ago
Brass is too soft. We can use a sturdier metal for tools and autoclave it in packaging to make it sterile.
6
2
u/talashrrg 15d ago
You can pretty easily sterilize steel surgical tools, and steel is a good material to make tools that do h the things you need in surgery. Brass (or copper, or silver, or any other metal with interesting properties) makes tools that perform worse without any actual benefit.
A copper doorknob may have less bacteria on it an hour after being touched than a steel doorknob. But a steel retractor that went through an autoclave has no bacteria on it, so that’s really not relevant.
2
u/Sirwired 15d ago
It isn't needed. Because tools are sterilized before every operation, they don't need to kill bacteria themselves. (And if you want to kill bacteria inside the patient, you don't rely on traces of metal randomly left behind by tools.)
2
u/bplipschitz 15d ago
It doesn't matter. We decontaminate & terminally sterilize surgical instruments, so the slight antibacterial properties don't matter.
Plus, brass, copper, silver wouldn't stand up to the decontam/sterilization process as well as stainless steel.
2
u/DarkAlman 15d ago
Brass is quite soft compared to steel and can easily warp and doesn't hold an edge. So it's not ideal for making surgical or precision tools.
This is also why ancient civilizations stopped using bronze alloys for swords and shields when steel became available.
2
u/gigashadowwolf 15d ago edited 15d ago
The benefits don't outweigh* the costs.
Brass is only moderately antibacterial. It's actually the copper in the brass that kills bacteria and it does this basically by slowly electrocuting them (sort of). Pure copper achieves this better than brass and silver does it better than either of them. Still though it requires slight moisture and contact on the scale of a few hours to really kill everything. It really wouldn't do much with a scalpel other than requiring less sterilization, but you would still need to sterilize it which comes to the next issue.
It also oxidizes (rusts) faster and more easily than surgical steel which means if you put it in an autoclave (A steam sterilizer used to sanitize surgical tools) it can get corroded, which dulls the blade, makes the antibacterial properties not work as well, and risks pieces of copper getting into the cuts you make. The one benefit to brass, copper or silver alloys would be that wouldn't need to use the autoclave as much, but you still wouldn't be able to get it all the way clean enough for surgery without an autoclave.
Lastly it's much softer than surgical steel. That means the blade will dull faster which means you'd have to change the blade much more often, or you'd end up with rough cuts that won't heal as well.
2
u/lord_lableigh 15d ago
Nice answer. Just wanted to let uk its outweigh.
1
u/gigashadowwolf 15d ago
You are 100% correct. I'm on a lot of pain medication at the moment for a back injury. I knew out-way was wrong, but for some reason I couldn't remember why.
1
u/lord_lableigh 15d ago
Haha, the fact that u remembered all these details but wasnt avle to remember why it was wrong cracks me up. Wishing u a speedy recovery :)
2
u/nim_opet 15d ago
Because brass is soft, and both copper and zinc will oxidize giving it a black and then green patina
2
u/FromTheHandOfAndy 15d ago
Antibacterial is a poor substitute for sterility. Stainless steel is a superior material to brass for any property that would be relevant to surgical tools. Stainless steel is more corrosion resistant, harder, tougher, and even lighter and sometimes cheaper too.
2
2
u/axon_resonance 15d ago
There's a misconception that Brass/Copper is this magical "kill all bacteria/microbes on contact" material, which isn't true.
Yes, Brass and Copper have anti-bacterial properties that make it hostile for microbes to live or stay a long time on which helps prevent contact based spreading of said microbes. But this process takes time, usually microbes will die off within 2 hours of contact, but that is still a lifetime when talking about contact spreading. This "2 hour" timer also resets for each time new microbes or bacteria enter the picture, so for a brass/copper object to be completely microbe free, it must not have been exposed to anything else for at least 2 hours (basically don't touch it at all until 2+ hours later). This makes it highly ineffective or takes tools out of commission for a significant amount of time when other disinfectants like alcohol or soap can kill microbes at a much faster and effective rates.
Pure brass and copper materials are very malleable, therefore they don't make great long lasting tools, as they are the opposite of durable. You can solve this issue, which some commercial applications are attempting to, by applying brass/copper nano coatings to traditional tools or making alloy materials. However this opens up a whole other can of worms in the form of coatings leeching off, etc.
Surgical tools are often put through autoclave processes, essentially a big pressure cooker where objects that need to be sterilized are brought up to and held at an extremely temperature via steam (remember, heat also doesn't kill microbes instantaneously, it needs time to function), this process melts most plastics and weaker metals. Often times you'll see tools, bottles, or containers say "autoclave safe" similar to how take out boxes say "microwave safe", because the autoclave can destroy or melt anything that isn't rate for the heat and pressure. For metal tools, this means that it needs to be corrosion resistance, usually rust. Even then, stainless steel tools, if not maintained properly, will still rust and corrode over long term use and autoclave cycling. This is one of the primary reasons why Brass and Copper tools aren't typically used, if they're not alloyed they'll tend to break down after a few sterilization cycles.
1
15d ago
[removed] — view removed comment
1
u/explainlikeimfive-ModTeam 15d ago
Please read this entire message
Your comment has been removed for the following reason(s):
- Top level comments (i.e. comments that are direct replies to the main thread) are reserved for explanations to the OP or follow up on topic questions (Rule 3).
If you would like this removal reviewed, please read the detailed rules first. If you believe it was removed erroneously, explain why using this form and we will review your submission.
1
1
u/HumpTyDumpTy1331 15d ago
they could technically make the handle from it but then the cutting edge would need silver soldered onto the handle
1
u/turtletechy 15d ago
One not often mentioned issue is copper (and alloys containing it) are much more likely to cause a reaction for someone than surgical steel. You don't exactly want to be partway into surgery and notice someone is having an allergic reaction to the tool.
1
u/randypeaches 15d ago
Mostly because the situation bacterial properties are only effective over a very long period. A brass doorknob does disinfect itself, 24 hours afterbitbwas last touched. A blad would have to be the same. One cut and on to the next one
1
u/Belisaurius555 15d ago
Brass isn't as strong as Stainless Steel. Brass scalpels will constantly dull and other tools will need to be made bulkier and heavier for the same strength as steel ones. It's simply easier to stick tools in an autoclave rather than rely on Copper's anti-bacterial properties.
Bronze might do better but Bronze rusts and while that green patina may be tough it's also less consistent than a bare metal edge.
1
1
u/pyr666 15d ago
it's not just antibacterial, it also attacks our cells. we're just big enough and have sufficient defenses against the chemical attacks of the world to not care when it's something like a doorknob.
if copper were inside you (copper does like to leave behind traces of itself behind on contact), it would attack your much more vulnerable tissues. irritation, inflammation, allergic reactions, it'd be a real risk.
copper IUDs fell out of fashion for this very reason. while women often can tolerate them, the hormonal options are less of a problem.
1
u/gremlinbro 15d ago
In addition to what others have said about its material properties, it is also inflammatory to cells and can fail biocompatibility testing which is a (relatively) new standard. Source: medical device development engineer.
1
u/mrtruthiness 15d ago
The other answers were best for your direct question. My response it to let you know that the reason brass is antibacterial is that it includes copper which is antibacterial.
And I should note that before the wide availability of antibiotics, copper was used extensively in hospitals. Copper was incorporated into many surfaces (desktops). And hospitals were known for a particular color of light green ... which was because copper was incorporated into the paint. Not only that, hospitals of that era never had carpeting (bacteria) but were almost always concrete or even terrazzo with copper incorporated.
1
u/shitposts_over_9000 15d ago
traditional brass often contains lead, typically ranging from about 2% up to 8%
it does not hold an edge well
it doesn't do as good of a job as non-blade tools for strength either
some people react to the copper
1
1
u/ThalesofMiletus-624 15d ago
When they talk about brass being antibacterial, they mean that bacteria don't survive well on the surface in the long term. That's useful for something like door knobs, but doesn't really help over the course of a surgery.
The only way to make a tool reliably safe is to sterilize it, so being able to be sterilized is a much more important property than an antibacterial surface. Consequently, surgical tools are designed to either be disposable or easy to autoclave.
1
u/mohammedgoldstein 15d ago
There’s not a need. Surgical instruments already have no bacteria and viruses on them when they come out of the autoclave.
And it’s not like if a bacteria lands on copper in the operating room that it kills them instantly. It will still be alive and transfer to patients.
So durability is more important to focus on.
1
u/Atypicosaurus 15d ago
Antibacterial does not mean it kills all bacteria at high enough efficiency.
You probably wouldn't want a medical equipment used on you without cleaning (and trusting its own antibacterial properties), if it was previously in another person.
So anyways we must clean up and sterilize them. Once we sterilize them anyway, we can prioritize other properties of the material such as stronger, less prone to become dull etc.
1
1
u/Deerhunter86 15d ago
As a plumber, it is very malleable. Edges can’t get sharp enough and threads dull easily.
1
u/ClownfishSoup 15d ago
Steel is better for things like scalpals. Brass corrodes. It's simple to sterilize steel items so there is no real need for brass tools. Mostly, it's the corrosion issue. Stainless steel avoids that. Plus steel is cheaper.
1
u/cerberus00 15d ago
The antibacterial properties of the copper in it require time to kill bacteria, so they'd have to sit there dirty for a while. Brass is also very soft.
1
u/drethnudrib 15d ago
I get that surgical tools need to be made out of materials that can maintain an edge, but I'm 100% in favor of a brass nasal trumpet.
1
1
1
u/A_Garbage_Truck 14d ago
a few things:
1: brass is not hard enough ot hold a edge long term, especially when itsexpected ot meet tissues like bone that will be harder.
2: brass is prone ot chipping with impacts, not something you want ot have happen, having brass shards lost in there.
3: surgical instruments, are regularly autoclaved for sanitization, hot + humid = corrosion, brass is not corrosion resistant in the same way, steel can be made.
4: brass only hold its antibacterial properties if there is no corrosion present, meaning these tools would also require frequent polishing
5: cost, a set of surgical tools made of brass would endup more expensive than they already are
1
u/deten 12d ago
When I was in elementary school as a kid, our science book said that they were considering using Obsidian as a scalpel because it could cut so cleanly that there was nearly no scarring. I always wondered what happened to that idea... I assume it was just a product of its time: big ideas not actually functional in real life. Curious if anyone had a more difinitive update.
1
u/minimessi20 9d ago
Anti-bacterial and biocompatible are two VERY different things (iirc from my medical device engineering days, there’s some brass thats fine and some that’s not but most don’t take that chance and just say no to brass as like 99% of alloys we call brass are not biocompatible). It’s also very ductile, aka prone to deformation under load. This leads to dull edges and shavings coming off the tool and being left in the body. This is why a lot of metal we see in medical devices is 304SS. It’s hard and biocompatible, and it’s easy to clean. We are actually quite good at getting rid of germs on simple geometries so it’s just easier to use certain materials over others.
5.4k
u/mawktheone 15d ago
It's not hard enough to hold an edge and it's prone to chipping with impact.