čas přidán 14. 01. 2023
I torture tested MDF vs. Plywood to see how they would hold up to water, weight and fire! The results were unexpected.
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Check out the original MDF vs. Plywood video: cs-tv.org/tv/video-Vwx3YivaPHk.html
As you can see from the comments below , whether or not to use MDF in a project is of great interest to the folks who clicked-in to watch your Vid . There are some really good comments below that include some good questions and discussions for possible add-on topics for you to explore ! Good job _SO FAR_ 👍!
Actually you weren't wrong totally. It's actually a special MDF looking Material called MD-X or MED-X that's made for wet areas, example-around sinks in cabinets. I'm a 3rd generation Wood Craftsman/Cabinet maker with !5-20yrs experience myself.
Douglas fir pine ? Marine plywood ? Missing? You get an f , do it over
Did you weigh the wood before and after?
both MDF vs. Plywood dont like water in the long run and both have there use for things ... if ou take a nice full wood shells you get the same over time ... but agian i only been a carpenter for +30 years, your testing was fun and good ...
My main observation with MDF is how it warps over time. It seems nice and strong at first but If I have a shelf made from MDF it will sag over time much worse than plywood with the same weight on it.
Agreed, especially if you put a bunch of books on it. The MDF will get saggier and saggier, but ply will hold up pretty well for years.
Add front lip made of MDF/Ply/Softwood/hardwood. For bonus points support it at the back AND sides.
I have some metal framed MDF shelves in the garage and I flip them every year or so. I’ve also painted them on all sides to try and keep the swelling from high humidity down.
@Colin Johnson I noticed that the warped plywood in the vide was turned upside down, which of course made it resist better. Your idea of flipping the shelves is of course the way to go, for that very reason. A little bit of "negative" warping reduces the load stress in the middle, until the shelf is warping down again, at which point the load is concentrated in the center. It is just basic geometry,
MDF paints so well, but it definitely needs ample reinforcement.
Fun bonus idea: measuring the difference in red water volume would help understand just how much is being absorbed by the pieces.
I was just about to comment saying he should have weighed the boards pre-soak. Good thinking
@tannertgf or measure the water in the jar before and after….
@MidnightDrifter10weight would be better as it controls for evaporation
we used the physical properties of MDF to save our basement in case of flooding. Two tracks of U-shaped aluminium on both sides of a critical doorway, just slightly wider than the thickness of the MDF-Board. A bead of silicone to seal the entrance. If water entered the basement the MDF expanded and closed the gap in the u profile stopping the water to intrude any further.
oh, very smart!
@Fix This Build That is it though?
I don't get it. I'll need to see some photos.
Yeah, I had this when I came back from holidays and a pine wood cellar door wouldn't open because there had been water pushing through the wall into the room on the other side and the door swelled when the water reached it.....
I made shelves a long time ago with MDF and they warped so hard it was more a roller coaster than a shelf even though there was very little weight put on to them (the vertical boards held pretty well which is interesting). I also made another shelve around the same time I made the MDF ones but this one was made from plywood and it is still standing strong even after putting a huge old heavy tv on it for years.
I used hardwood stair treads for rebuilding a bookcase 15 or 20 years ago. Those shelves are still as straight as they were new, even after being fully laden for all that time.
I watched this and the previous video at cheap desk with a painted MDF top. When it gets a tiny scratch, any amount of water (condensation on glasses, spilled drinks, or even from sweat in the summer) causes it to swell and create bumps. There's no fixing it. Stumpy Nubs had a tip to use CA glue to re-seal the mdf, so it won't get worse in those locations, but the desk has pock marks all over it now.
I had the same issue with a premade composite bench top that's sealed 1/2 flake board w/inner solid 2x6 construction. I skimmed the entire surface with epoxy using a pc of thin styrene about 4x6" and (1/16,.062 1.5mm thk.)Try to not leave ridges as you smear coat by overlapping. Then sand down the micro ridges leftover with a 1/4 sheet sander after its cured and do this till your desired thickness is achieved. Last coat sand progressively finer till 400 or better for a nice low shine finish that's ready to beat up again! LOL EDIT: Sand surface first to 220 or 320 before epoxy coating and between each coat or it will not adhere to the previous smooth surface and chip/peel more easily.
I still think you need to test the MDF deflection over time. I'm reasonably certain if you put the MDF shelf under a load of a full month, it will deflect a lot more than when you first applied the load.
This is the biggest problem for me. We all know about the water capabilities, or lack there of, of MDF but not many know of the issue of creep. Under a consistent pressure MDF will slowly deform to a much greater degree then plywood. I've seen MDF shelves with little to no weight on them that where several years old and sagging several inches in the center.
@Jason Harrison Can confirm - I'm looking at some sagging MDF shelves right now. An even tougher comparison for the MDF than plywood would be solid pine shelves. Having all of the long grain aligned with the direction of bending should make them stiffer than plywood.
That happens on my book shelves. I take the books out and flip the shelves over every now and then.
@Mark Burton I've wondered how well it would work to get a steel bar a little thinner than your table saw kerf about 1/2" tall and epoxy that in a grove near the front and back of the shelf to stiffen it up. I just wonder if the the epoxy would pull out of the MDF over time. I guess you could drill several small holes and then drive some pin nails in the front edge to hold better. On the back side you could just screw a 3/4 x 1/8" steel strip since that wouldn't be visible.
I used to do a quick and easy closet organiser. All the shelves are sagging. I made another from oak plywood. Its still straight as can be.
At our shop we sometimes use “marine grade MDF” that’s more stable in situations with water exposure; we use it mainly for doors, in rooms that get lots of humidity
Oh yeah “Medex” , more garbage!
It would be interesting to see how exterior grade and marine plywoods compare.
exterior grade plywood doesnt exist. marine ply does.
Brad, this video was very useful and I thank you for all the time and effort you put into it! But seriously: this was fun, you had me laughing out loud, for real!
Glad you enjoyed it! 😀
in what way was this video useful?
@Fix This Build That how would OSB fare in this competition?
I always appreciate your videos! If you would have flipped the plywood over so it bowed downward, it would have likely been weaker than placing it with the bow upwards. This is the same reason they design flatbed semi trailers to bow upwards when they're not loaded.
considering he had the bowed side flipped down for the MDF, i feel like this was a really ignorant mistake.
Because the arch is the strongest support for a span...
great video! The biggest problem I have with MDF is that even though it seems like it can hold a lot of weight, it can't do it indefinitely. little by little it will sag more and eventually fail. At least thats my experience with it.
You have to be really careful when applying heat to MDF. Formaldehyde is usually part of the manufacturing process.
Great job! Would be Intersting to see a similar test with exterior sheathing options like OSB, OSB with a weather barrier, and a zip type board. Could even test tape applications on joints, etc.
Very interesting test :) You should also try to see if those smaller boards that were completely submerged would snap under load too. It would require a different jig, but it'd be interesting for sure :)
Re. the water tests; it would be interesting to see the results using marine ply (as used in boat building) which is made with a glue with resistance to long term water exposure, even under pressure (as when it forms the hull of the boat).
My experience is the same as the outcome of this video except for the solid wood edge version. I haven't done that, but I will now. I'll be using mdf in different ways now. Thanks Brad!!
Would be interesting to see a comparison between green MDF and ordinary MDF.
Interesting and informative video. I work on cabinets (mostly refinishing existing cabinets) and I have the same experience with MDF shelves that I'm reading in the comments about warping over time. I've seen it on both ply and MDF but is certainly more pronounced in MDF. If we don't end up replacing the shelves for whatever reason, I just flip them over.
Brad-always appreciate these kinds of educational videos; am wondering if you could do an educational video on LEDs 101? I know you’ve done a couple videos (which I’ve watched) on putting LEDs in your work but feeling like I can’t find a soup to nuts video from design to installation on LEDs in woodwork and think you’d be great at teaching something like that. Thanks for any consideration you give this idea.
If the materials are in danger of getting wet, use marine ply or waterproof (outdoor) MDF.
I don't even work with wood at all and I still watched the whole video. Thanks for being both educating and entertaining!
Great video! One interesting thing to add to the water soak test - you could weigh the water cup before and after the test. There could be a difference between surface and internal soaking. Weighing the water would give you the amount of water being held in each wood/mdf sample.
Brad, thank you very much for your time and effort xo
Good content on these two videos. I'm curious what the absorbion weight is on the various materials. Also what the duration of time is to get each material back to near-new moisture content. Could also use a wood moisture meter to measure. Just some thoughts.
Brad, I would have liked to have seen one more shelf tested - the radiata plywood with a hardwood face... I suspect that would be quite a bit stronger than the MDF/hardwood shelf.
I would love to see MDF vs. White or yellow pine experiments. Thank you.
I know it's not really the same but I would have been curious to see how OSB would resist these tests.
Informative and fun! I just wish you'd done the plywood at the end as well to show the load-bearing difference between them.
Brad, thank you very much for your time and effort.
Two thoughts: One, I've noticed that both MDF and particle board fail slowly when they have a constant load on them. Shelves that seem fine with a certain weight when built will gradually bow and eventually break over the course of years. I suspect it has to do with changing humidity, but that's just a guess. Second, what is the water resistance rating of the glue in that plywood? I think most ply now uses water-resistant glue, but I know that if you soaked a piece of older standard plywood overnight you would just have a stack of veneer flitches when it dried out. MDF has its uses, but I wouldn't use it for anything that is load-bearing or that has a high probability of getting wet. These tests pretty much reinforce my opinions formed over several decades of using the stuff.
I’m digging the Mr. Brad science dad with this testing 😂. Also cool slo-mo at the end where the concrete bags were levitating. Good fun!
Coming across this was interesting; I didn't read down the comments to far as it was just talk about the strength and advantages of plywood VS MDF, but I wanted to bring up the potential of mold growth in MDF and particle board.
An interesting and well-conceived experiment. Good job! I wonder what observations you might have recorded with a sample of marine-grade plywood? Hmm.
15:39 lol how excited you got at the failure. Love it! Great tests Brad!
I didn't expect the shotgun crack, though it'd just slowly tear. So I wasnt ready for that 😂😂. Happy New Year, Matt!
The plywood that my company gets, comes apart from humidity change. I think it's held together by hope.
There are many grades and types of plywood.
It would be great if you could have weighed the wood to see how much was actually absorbed. Also, maybe some moisture content readings at various time points.
THANK YOU!! My girlfriend has always thought I was using the word 'Deflected' wrong when doing DIY stuff around the house.... YOU sir have proven her wrong.. 😎😁
With MDF as flooring for trailers, I tend to fall through them with more frequently it seems.
One test that would be good to do is the combination of water and heat (maybe the process used to remove wood veneer with a damp cloth and an iron)
The thing that's hardest to test, but that I've observed in the real world is how in humid environments over time the ambient moisture tends to soak into MDF and make it sponge up, and weaken then fall apart. Which is why when I was looking at vanities for my bathroom remodel, I looked specifically for wood construction and immediately nixed any that had any mention of MDF
I think the big takeaway is that each type has its own uses. Some shared, some not. It's another tool that needs to be selected by use case.
You also have to take into account that the majority grain in the plywood was crosswise, not lengthwise, which made it weaker and more likely to warp.
There's a water resistant MDF called Armorite. I've never used it before and would be interested in seeing it tested.
That hardwood front on the MDF shelf adds a lot of strength.
Think of a main use of MDF - kitchen cabinets. The base cabinets sit end grain down on the floor, when the leak occurs, it is sitting in a puddle of water which wicks right up into MDF and it does indeed turn to sawdust. Bottom shelves of cabinets do the same thing. You put your blanket over a relatively small surface area. The fact is that when a bathroom or kitchen leak occurs, it typically covers not only the surface but soaks into the edge grain and end grain as well causing it to warp separate and yes, turn to sawdust. MDF should never be used for cabinets in wet areas, but everyone does.
It depends on what MDF you buy because of the amount of resin used to make it
We call it Major Deficiency Fixer because MDF is so versatile, I even use drywall mud on it to blend it into walls
Thanks for testing the plastic shelf supports - I've always been leery of the ones supporting my 1x6 pantry shelves with, like, 5 lbs on them. Now I know I can jump up and down on them ;-) Not quite.
I would've been interested in the MDF in water with the same two coats of protection that went on the ply. 👍
Thank you for this video - very informative. I really liked how scientific the experiments were presented and would like if you went a bit further. When you put the flame to the wood, it reminded me of the Japanese method of preserving wood posts that go into the ground by charring to create a thin carbon layer that resists water absorbing which prevents rot. I am willing to bet folding money that you could come up with an experiment to show or debunk this. Thanks again.
This was so entertaining to watch! Scratched that geek itch with your %Swole chart for sure. I’m even a non-builder-handyperson type and this was great to watch. Well done
Good video as always. I enjoyed the various tests you performed and have no complaints. I do wonder how well a “MR/moisture resistant” mdf such as Medite MR or a pressure treated plywood would have faired. I know we don’t usually use pressure treated plywood much as woodworkers but I do use MR style mdf on occasion. I am a fan but I’m not THAT heavy! 😊 Ron
The mdf held 600lbs before the only reason it failed the last test was it was spread out more compared to the previous
Resided a house w/ an MDF like faux t1 11 of sorts. That Georgia Pacifc siding we replaced was falling apart lol. Over time plywood will (can) last a long time when used appropriately.
Brad, thank you very much for your time and effort
5:35 I hope you used metric units for these tests. It's pretty each to see how much more accurate the millimeter scale would be in this test alone. Plus metric is much better overall for all use cases, except for some historical context.
We Americans wouldn't understand...
wow look at all those plans you have. and reasonable! i'm coming back to get some as soon as i have stuff sorted that i have room to build!
That "Slo-Mo" at the end was incredible. When the MDF broke, the halves released their stored elastic energy immediately. The broken ends from the middle made contact with the floor, before the concrete bags even began to move! There were some great physics going on there. For the next test, try taking identical samples of the 48" long boards, load them to 200 pounds, then leave them loaded for a week. Remove the loads, then immediately measure the warp. After a day, measure again, and see if there is any elastic memory. Very often, you can overload a shelf for a short period of time, (someone sits on it for a moment) and it returns. That much weight over time, can cause a gradual increase in sag. Will it straighten out when unloaded or not?
One of the tests we used to do, when testing for the effects of moisture on a building material, is to run wet/dry cycles. More than long-term exposure to moisture, I think you'll find that the number of wet/dry cycles a material can withstand will surprise you, especially with mdf vs a wooden laminate like plywood.
Yup. I used to work for a building products company and spent at least one day a week in the lab, running similar kinds of tests.
Brad, thank you very much for your time and effort 💋
Brad, thank you very much for your time, and effort.
There is a very big different WEIGHT DISTRIBUTION between a stack of bags width wise in he center, and two stacks side by side cross wise. With the two bag stacking there is much more weight on the ends of the shelf supported by the cleats.
Mdf is bonded with a wax and resin binder with high temperature and pressure, which is most likely why the surface resists water, but the cut edges allow more water in. As with any wood end grains not sealed, allow water to soak in due to the structure of the wood being straw like fibers
When it comes to shelfs I have found it's about what happens after 5 years. And often the shelfs that didn't warp at all and weren't seriously loaded end up sagging tremendously. Take the shelf off and it is a permanent bend.
Kinda wish you'd have tested to failure on dry vs wet plywood & mdf, like that last test. Also it's probably worth mentioning in the swell tests, that that massive amount of swelling will do things like rip screws through MDF. Even if your shelf doesn't outright fail, it'll weaken and loosen considerably after even limited moisture exposure - not because the board itself is substantially compromised, but because the swelling and shrinking process is so extreme that it shakes the whole structure up.
You should consider pressure points when adding load to the shelf. If you add 1 row of cement bags to the middle it's more concentrated in the middle. But with two rows of bags, the bags will neal to themself and create the pressure point to the end of the both sides of the shelf. So you cannot compare the results of 1 stack vs 2 side by side stacks.
Brad, thank you for your time and effort :)
Nice in theory, but I've had a few leaky hot water tanks fall trough carpeted mdf floors over the years..
Not only is material strength important but geometry plays a far greater role. That's why aluminum structures can be so strong. Due to geometry. ie. diameter of tube or square stock, I or H beams, trusses, and triangles, and combo of all of them. You changed the geometry dramatically by adding the hardwood edge.
In regards to the wet shelf test when you were wondering why someone might have water on them long term - if someone raises houseplants or has a seedling nursery then you can't avoid a near permanent water presence on the wood. My grandmother did both the plywood shelves all had water stains.
You could ask your viewers to do wood test and send them to you to comment on. It would be a way to get them to be involved and more invested in the process. It would also give you free content.
So the take away here is, don't let wood get wet. Awesome, thank you.
Brad's reaction at the end was so unnecessarily over the top, but so wholesome. He seems like the type of guy to be genuinely enthusiastic about _everything_. Brad, will u be my dad?
Plywood was placed bow-up. The bow, acting as an arch, is the source of the increased strength. Had you placed it bow-down, it would have deflected more. Thanks for the video. Was a lot of fun. First time I've seen your channel.
I'm a bespoke furniture builder in Brazil. Here almost 100% of woodwokers use MDF foi furnitures and everything works perfectly. Sure, MDF has its owns limitations, but is a great material. Pretty reliable, has some great textures and colors, no need to caulk and paint (here we use mostly melaline covered MDF, unless you want a Lacca finnish). Plywood it's most expensive here and need more work to get the same visual result. Great video though.
Plywood comes in interior, exterior, marine, and treated. MDF comes in many different types also. You should also show OSB and particle board.
There's a product called tricoya that is basically an acetylated mdf whick is submersible. You can also get radiata pine that's processed the same way called accoya
6:43 Deflection implies stiffness and not necessarily strength. Something can deflect alot but ultimately take more load.
You should've thrown a sheet of MDO into the mix. Since it's got an mdf overlay. From my understanding mdo is pretty much waterproof. It's an exterior glue used instead of interior, which I know will play a major role in these style of tests
The upwards bow of the ply probably functioned akin to prestressing, reducing the deflection by adding forces acting against the added weight.
I work at a plant that makes plywood and MDF, MDF is very very heavy and sturdy. pretty neat to see this
love the video, only question, ply without the edge banding is better than MDF without, what about ply with edge banding? for those of us that like the math's (sorry for those that don't, but I'm an engineer too), it would be cool to see the results of ply vs MDF both with edge banding.
Interesting, Brad. The arch in the plywood actually strengthened it. That's why it had less deflection. Look at a large dam and they're arched against the water pressure. Also, you were having entirely too much fun with that torch. Bill
yeah, after I saw the bow I figured it might be even stronger....though ugly, lol
@Fix This Build That Look at flat deck semi-truck trailers, you'll see unloaded they are parabolic in order to increase strength and resist deflection. Arch up is much stronger in your test case, and will deflect less.
now if that was placed with the arch down, it may not have been as strong
I kinda wish he'd piled concrete bags on the charred boards, to test for strength. I mean they're obviously beyond repair regardless, but maybe one is just a little more likely to Hodor longer than the others.
Or bridge supports...
Interesting tests. I would like to see a water test while under load, because of course the real world failures happen when something is under load AND getting soaked by water intrusion.
Excellent detailed comparison. Oddly there's been a record number of flame thrower injuries since this video aired. Something to do with not wearing proper protective equipment such as flame retardant clothing, gloves and goggles. :()
Can you do some water tests with PAINTED wood? Like if you were to make a piece of furniture and then paint it, how would it last between the wood types? Just like with the varnish test but paint instead.
What about doing radiata ply with hardwood edge band? Would it be a better comparison to test that against the MDF w/ hardwood edge band?
So for the plywood loaded test, when you put the shelf in with the bow "up" it acts as a pre-stressed shape and resists deflection. If you had installed it the opposite way (bow down), it would have deflected more.
Would the hardwood facing on the MDF also block the edges off, protecting them from the water?
This was cool and funny. I've never made a shelf or a bookcase out of either plywood or mdf, though. They both sag a lot. How about a test with solid lumber? Wide glueups are easy, and if you want easier, you can buy solid wood shelf board, already planed to width and thickness at most big box home stores. For rough work, you can just use 2x12s side by side.
years ago I made a sort of drawers and towel holding table to some customer's ideal specifications( some designer friend of theirs's said to used mdf because it paints well) . The whole thing had to be made from MDF but I argued with my boss about the design ( specifically the lengthy span as with all the drawers on top with no bracing/legs in the middle to keep it from sagging or at least to only use mdf on the outside that would get painted). well it went out and came back because when they put the marble top on this monstrosity they realized the thing sagged a good half inch in the middle and was noticeable with a slab of marble for the top so I had to add legs in the middle to support it like I originally said.
The last plywood deflection test had physics on its side. I would have liked to seen it tested with the bow down as well.
My thoughts exactly, I’m p sure it would have bowed down when it was wet, right?
Thank you for a fun and interesting video. I really enjoyed watching it.
You know, you went to town on the wood with the flamethrower, so you should have sawed into them to see how deep the burns went
Would be interesting to add particle board to your tests. When I used to design and build melamine furniture, we almost always used MDF for verticals and particle for horizontals - especially where we needed less flex, like shelving.
Once partial board wood gets wet... It's completely useless! The swollen wood breaks the bonding agent and it reverts back to just sawdust.
Yeah, it definitely wouldn't do well with submersion... I was mostly just pointing out that it is "better" than MDF in certain applications.
Also because of the nature of plywood it will be stiffer in one direction than the other, depending on which axis has the most cross grain ply's.
Great video! As far as moisture resistance goes....30 years ago I had Formica counter tops made. The counter top guy told me to paint the underside of the back splash with oil base kilz or oil base primer before he installed it. He said this would keep the particle board from swelling up if the silicon caulk seal should fail. I also paint the underside of the front (especially near a sink). I have had great success with both applications. I would also paint the side of the particle board on the side of the cut out for a sink. I would paint any wood product for this kind of application. (I was a professional painter. I would understand if people are saying, they paint everything.)
I think it's ridiculous that the cabinet under/around a sink is made from cheap particle board. You _know_ it will get wet eventually. If I were making custom cabinet work, I would make this one compartment at least out of better material. When I had the opportunity, working under the sink, I laminated a sheet of contractor plastic along the bottom and a few inches up the sides.
@John Długosz - I do not think the original comment was referring to the cabinets; particle board is the typical material that is used when a laminate countertop is made, so I think the original comment was strictly referring to the particle board that is bonded to the Formica sheet.
@Steve Babiak, You are correct in what I was referring.
@John Długosz I think it's ridiculous to make a cabinet around the sink of any kind of wood. I have a sink and countertop completely made of stainless steel. It does not wear and does not swell. This has been common practice in my country for decades.
Brad, than you very much for your time and effort. This was great.
Really interesting on the MDF with hardwood face, might actually consider that for shelving when I wouldn't have before.
You can make plywood much stronger by adding a hardwood face as well. Plywood shelving is much better than MDF, especially if it isn't a built-in and will be moved occasionally.
I've often used edged mdf for shelves with excellent results.