I have a broken LEGO piece that I want to try to superglue together.

Broken LEGO door

It would be A LOT easier if I could do this on a flat surface and even let it rest there for a while afterwards. But if I do that I will most likely glue the piece to the surface. Are there any materials (that are commonly found in households or at least easy to find) that superglue does NOT stick to, and which I could use for my work?

  • 16
    Well, superglue won't stick to Lego… it will hold blocks together reasonably well, but it doesn't actually properly 'stick' to the plastic they use. Your door will just fall apart again in no time. You need a solvent - See bricks.stackexchange.com/questions/1037/…
    – Tetsujin
    Nov 21, 2022 at 7:49
  • 1
    Acetone (bricks.stackexchange.com/a/1286/13646) seems to be one solvent that works, but I would test out how well it works first. Maybe deliberately break a test brick and try out if it works.
    – Nelson
    Nov 21, 2022 at 9:07
  • 10
    This might be worth asking on Bricks.SE because, lego. Is one of those rare questions which are totally on-topic on two separate SE sites.
    – Criggie
    Nov 21, 2022 at 10:42
  • 13
    Coming from Bricks.SE. Any glue you use will not be contained in cracked area and will squeeze to surface. Maybe even discoloring the plastic. Since this door is from LEGO DUPLO set designed for youngest kids (which can still put things in their mouth) I strongly suggest you to getting a replacement instead. Via LEGO Customer Service (i'm sure they will be happy to assist) or buy at Bricklink.
    – Alex
    Nov 21, 2022 at 13:43
  • 3
    IME, the only surface super glue/CA glue won't stick to is the one you are trying to repair. And the only surface it will stick to is the things you don't want it to stick to. Sort of like tape. Nov 22, 2022 at 20:07

7 Answers 7


HDPE (high-density polyethylene) is a material that superglue does not stick to at all. You can find sheets of it at hardware stores and online retailers such as Amazon.

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  • 2
    You may also find common household containers/products using the HDPE material. Drink containers (orange juice) that are not transparent are likely HDPE.
    – fred_dot_u
    Nov 20, 2022 at 23:26
  • I just quickly checked some generic stuff/trash that I have, and there was no HDPE. Plenty of PP, some PET, and an occasional LDPE. But I didn't find any HDPE. Would LDPE also work?
    – Vilx-
    Nov 20, 2022 at 23:53
  • 3
    Kitchen chopping boards - the softer plastic ones that don't blunt your knives - are non-stick to most glues.
    – Tetsujin
    Nov 21, 2022 at 7:52
  • 1
    polypropylene is also pretty good against superglue (there's a special "all plastics" version with a surface activator if you do need to glue PP, as I've had to in work). It's worth using thin material because then you can peel it off the back of the workpiece.
    – Chris H
    Nov 21, 2022 at 9:32
  • 2
    @Vilx- At least in the US, milk jugs are commonly made out of HDPE. Sometimes they're PET, though.
    – Hearth
    Nov 22, 2022 at 16:17

I usually collect in a box the backing of stickers and other adhesive tape stuff (like double sided tape) as they are especially made to not stick to glue.

They have the added advantage that they can be peeled off easier even when they stick a bit as they are flexible, and in the worst case you can scrub them off with the right cleaner/solvent.

  • This is absolute genius! Why did I never think of this before?? I'm forever repairing kids toys and you just made this 100% easier!!!! Nov 22, 2022 at 22:24

Almost all ‘super glue’ brands are an ethyl cyanoacrylate adhesive (ECA), with some form of gelling agent to make it easier to work with and occasionally some rubberizing agent to improve the shear strength. Such adhesives set by polymerizing. This means that a surface not ‘bonding well’ is dependent on two factors:

  • Whether or not the adhesive actually polymerizes with the surface.
  • Whether or not the adhesive can polymerize in such a way that it can ‘grip’ the surface.

As a general rule, ECA does not actually polymerize very well with most things. Baring other layers of cyanoacrylate adhesives and a handful of very specific types of organic molecule, it almost entirely relies on ‘grip’ strength instead of polymerizing with the material. This is why it’s so good at bonding to stuff like leather, fabric, wood, or coral (at a microscopic level, these all have very rough surfaces that the adhesive can work into and grip).

However, this has a notable side effect: ECA is not very good at bonding to very smooth surfaces.

Based on experience, smooth sheets of glass, high-density-polyethylene, PTFE (‘Teflon’), and even some forms of ABS work very well as work surfaces because of this.

That said, this same property, together with it’s relative flexibility and low shear-strength, means that ECA is not actually very good for fixing LEGO pieces. In particular:

  • It does not really polymerize all that much with the particular blend of ABS that LEGO pieces are made of.
  • Because of the specific blend of ABS involved, when a LEGO piece breaks it’s often smooth enough at a microscopic level that ECA will not grip it very well.
  • Even if it grips well, the flexibility and low shear strength of polymerized ECA means that the piece will tend to flex more than it should, and will almost always eventually fall apart again on exactly the same break.

Additionally, some of the additives may damage or discolor the bricks.

Because of this, I strongly second the opinions of the various commenters on the question: You’re far better off using a solvent to ‘weld’ the pieces back together. Many ‘plastic cement‘ type things will work for this because of their typical composition, as will acetone. However, doing this ‘right’ takes a bit of practice, especially if the pieces do not fit together perfectly, and I encourage you to break a few other bricks to actually practice, as well as to test how well your chosen solution works.

I have personally had decent luck with pure acetone (you can usually get this from hardware stores or beauty-supply stores, the 70% stuff sold as nail-polish remover in many supermarkets does not work well), and better luck with methyl-ethyl-ketone (MEK) (which has actually been used by LEGO for making builds permanent), though MEK is harder to get legally in many places due to drug regulations (it’s on a number of drug-precursor chemical lists) and is a bit trickier to work with because it’s a much more effective solvent for ABS (IOW, you have to be quick and precise to get good results).

Regardless of what you eventually choose to use for this:

  • Always do it in a properly ventilated area with appropriate protective gear (at minimum, disposable gloves made of something the solvent won’t dissolve). Many of the things you could use for this are nasty toxic.
  • Always let it set for a while before testing the joint. The solvent has to pretty much completely evaporate for the joint to set properly. Testing it too soon will just break things again, and quite often in a way that’s more difficult to fix.
  • Always let it sit for a few days after testing the joint before giving it to a child. You want to be absolutely certain that all of the solvent is gone before a kid puts it in their mouth.
  • 1
    I haven't tried with ABS, but in general when I am solvent welding plastic parts together, I prefer to dissolve extra polymer into the solvent first, to give it a thicker gel consistency that is easier to work with. In this case I guess you'd have to shave bits off a sacrificial brown lego
    – timeskull
    Nov 22, 2022 at 17:40

Try testing the superglue on wax paper.


Whenever I glue up anything in my woodworking hobby, if I have something in contact with the glue line, I cover it in packing tape. Clear or brown, doesn't matter. Works with regular wood glue and 2-part epoxy. In general, glues don't stick well to plastics, particularly smooth plastics. That's something to keep in mind. A scuffed up, scratched up surface may bind somewhat to the glue since it will provide something for the glue to flow into.

  • I was going to write this. Clear Scotch tape (the kind that's super smooth and shiny) also works.
    – Esther
    Nov 21, 2022 at 16:33
  • Masking around the seam with tape can help prevent glue squeezing out and dribbling down the surface. Just pull off the tape and the excess comes with it. Much easier than trying to sand a dried glue blob off the surface.
    – bta
    Nov 21, 2022 at 23:35

Try using foil, thats what i usually use, also wax paper, or masking tape, but curious why this lego is so important?

  • 1
    'cuz I'm too lazy to look for and order new pieces instead of broken ones. 😅 And maybe they're out of stock (it's an older set). And I just want to try to see if I can. :)
    – Vilx-
    Nov 21, 2022 at 16:46

Just use a "new" non-stick pan...

Definition of "new":

  • no scratches
  • smooth interior (I.e no bumps, ridges, ...)

Actually the cheap ones should work best.

  • 5
    I'm not sure I want glue on things which later come into contact with food. Nov 22, 2022 at 0:42
  • 2
    @PaŭloEbermann CA glue is bio-safe, and is used frequently in medicine as an alternative to sutures.
    – Aaron
    Nov 22, 2022 at 17:51

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