Paraloid B-72
en.wikipedia.org

・

192 points

・

Ariarule

・

3 days ago

39 comments

mooman219 ・ 16 minutes ago

Oh I've used this personally! I had various surgeries that removed various amounts of bone from me and I asked to keep the bones, which they allowed! I wanted to preserve them in case I wanted to make some esoteric jewelry and it lead to paraloid B-72.

It's quite wonderful. I dissolve the paraloid B-72 in acetone (1 part B-72, 8 parts acetone), then soak the bone in the acetone for about an hour, let the bones dry, and then suddenly they're solid and strong. You can adjust how much acetone you use for how thin/thick you want the fluid. Bones are porus so I opted for a thinner solution and it worked great. It was also really cheap.

CarVac ・ 6 hours ago

Heh, I upvoted this a few days ago and it must've gotten on the second-chance queue.

Links to obsure but interesting Wikipedia articles are some of my favorite HN posts.

Xmd5a ・ 6 hours ago

Could this be used to 3D print supports ? For now, the only thermoplastic I know of that can be used to this effect is HIPS in conjunction with d-limonene.

zdw ・ 7 hours ago

This is the most esoteric post I've seen on HN in a while.

How many museum curators who need non-yellowing flexible thermoplastic are there on here?

  • aejm ・ 5 hours ago

    This post has exactly zero relevance to my professional career or personal projects, and this is exactly the type of esoteric content I love about HN!

  • boppo1 ・ 7 hours ago

    Oil painter here, this is news to me and if it doesn't dissolve in gamsol this is EXACTLY what I've been looking for for about 2 years.

    • bfivyvysj ・ 2 hours ago

      What's the application?

      • uxhacker ・ an hour ago

        It is used to strengthen materials. For example if plaster has crumbled, or the paint on a canvas has become flakey, or wood rotten, Paraloid B-72 can be used to hold everything together. The issue is that generally it is not reversible. Therefore one should always look at varnishes that can easily be removed and reapplied, but sometimes only Paraloid can hold everything toghther.

    • card_zero ・ 7 hours ago

      I followed the link to flexographic ink, and now I'm wondering whether boutique fine art flexography could or should exist. Like lithography, but more plastic.

  • uxhacker ・ an hour ago

    The issue is that it does yellow but after 25 to 50 years. The challange is that it is very difficult to reverse.

    On the restoration of my house I allow its use on very specific cases. It very useful for example in strengthening wood that has rotten. Sometimes Paraloid is the only thing that can be used, but it needs to be used with care.

    • greygood ・ an hour ago

      It does not turn yellow, Paraloid B66 does. B72 has a low Tg, 40°C, so it can soften and creep when warm

      • uxhacker ・ 12 minutes ago

        It does discolor over time. The point is that one should be thinking about the impact over centuries and not years. It needs to be used with care and other alternatives need to always be considered.

        For a painting or building that has survived for half a millennium we need use methods that will preserve the object for another 500 years.

        Too many times I hear people say we will just use Paraloid.

      • lollapalooza ・ an hour ago

        Didn't really know of the different 9(!) versions of it. Thanks for pointing it out.

    • lollapalooza ・ an hour ago

      Agreed. My gf uses it regularly as she's a furniture restorer, finding the definition here it's a bit of a surprise, though. Great, unique material.

  • glimshe ・ an hour ago

    Not many, but there are a few amateur and professional musicians here benefitting from better piano hammers made possible by Paraloid B-72!

    Note: I thought this was about Polaroid, not Paraloid, at first!

  • kazin1870 ・ 7 hours ago

    I use paraloid all the time, a bit surprised to see it posted here but I’ll support it.

    • boppo1 ・ 7 hours ago

      I'm new to it and having trouble finding guides:

      - how do I apply it as a coating? I want it to be ~ 1/6" to 1/8" thick and as hard as possible

      - will turpentine dissolve or soften it?

      • chromacity ・ 7 hours ago
        ・ 2 more

        It's a relatively soft plastic and I don't think you can realistically build a uniform, good-looking layer that's 1/8" thick, if that's what you mean. If you need that thickness, high hardness, and nice appearance, I think your best bet is just a sheet of glass or acrylic on top.

        It can be used as protective varnish, but that would be a very thin layer, probably 0.1 mm or something like that.

        • boppo1 ・ 7 hours ago

          Does it not level from gravity like other resins?

      • greygood ・ 32 minutes ago

        Purchase as crystals and dissolve in acetone or ethanol to desired concentration. It will self level based concentration, allow to evaporate before applying next layer

  • CarVac ・ 6 hours ago

    I've done some DIY piano maintenance and I saw what was presumably this available to firm up the hammers. My piano needs them softened, though.

    • clort ・ an hour ago

      Yes it mentioned firming piano hammers in the article. From what I remember, a piano hammer is a shaped piece of wood (or several?) with a leather strip around the striker part? What is the difference for you between hardening and softening the hammer, and how would it be done with this .. is it penetrating? (acetone base would enable that, it is used for carrying chemicals through a surface). Could you soften the hammers by replacing the leather strips, or soaking them to loosen & expand the presumably compacted fibres?

      In my wider life in the UK, speaking to people associated with pianos (from a piano tuner, to school premises teams), it is often not worth the commercial expense to repair old pianos unless they are of particularly good quality or have some sentimental value.

  • colordrops ・ 7 hours ago

    They should make non-yellowing transparent phone cases out of this stuff.

0xbadcafebee ・ 7 hours ago

Huh. So it's a stronger, harder, less brittle, clear wood glue you can dissolve with acetone. Neat!

aidenn0 ・ 7 hours ago

How does its strength compare to MMA structural adhesives? What materials is it compatible with?

  • shermantanktop ・ 3 hours ago

    My only expansion for MMA is “mixed martial arts” and I’m not particularly familiar with it. Maybe there’s a wrestling move called the “structural adhesive”?

    • clort ・ an hour ago

      methmethacrylate (ie acrylic)

Joel11 ・ 4 hours ago

Thanks for Sharing this information.

FpUser ・ 7 hours ago

Am I the only one that read it as Polaroid ;) ?