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Comment by dotancohen | Hacker News Reader

Sugru was the base for so many of my hacks from about 2005ish to maybe 2020. But it has become so expensive, and the new formulations so unreliable, that I am open to almost any alternative. Even the homemade cornstarch based formulations.

I still have a stack of things that I'd love to fix with Sugru, hoping that the old Sugru may someday be available again, or a good alternative could be found.

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I switched to kneadable epoxy putty about a decade ago

it's not the same formula by any means, but there's a large variety of putties with different properties.

my current go-to is "Polymeric Systems Kneadatite Blue/Yellow Epoxy Putty Tape 90cm Green Stuff"

Thanks. Can you tell me more about its properties after curing?

Right now, I'd love to make a custom earpiece for my smartphone - something I've done with Sugru in the past. It needs the material to be relatively rigid yet pliable after curing. It also needs to be sticky enough to bond to the phone case (I don't bond them to the phone glass anymore).

Thank you!

The one I linked is a rigid solid that is firm enough to sand & file.

I wouldnt consider it pliable after curing.

Thank you.

If you don’t need the stretchiness of silicone, thermoplastic might be a good answer. You can get little thermoplastic beads that soften up in hot water or under a heat gun. After cooling, they dry quite hard.

That might work for some purposes. How hot do they need to be? Will I be able to mold them with my fingers? Or will I need to make a mold? If I need to make a mold, out of what material?

Thank you.

It needs ~60℃ . Immediately after pulling it out of the hot water it might little bit too hot and sticky, but after cooling a little bit it will become less sticky and cool enough to safely touch with hands.

Thanks, this looks like it might work for some of my use cases.

Thank you!

The old cornstarch + silicone bathtub sealant + spritz of vinegar solution has been a mainstay for me.

Can you tell me more? What does the vinegar do?

Thank you.

One of the reagents (a byproduct actually of the curing process for silicone caulking) is acetic acid (vinegar), which stabilizes the plasticizers. Just a hair more makes it a little more "pliable" for a little while longer while you mold the final product in my experience. You only need a tiny bit, a dilute spray bottle of white vinegar is enough -- It's useful for other things too.

YMMV, it appears to be dependent on what style of silicone caulking you use.

I see, thank you.

For making enclosures, I use my 3D printer. It's not a replacement for sugru, but let's you get a lot of the same tasks done in a different approach.

Baking soda and super glue. Or just carbon fibre and laminating epoxy...

I have had superglue and baking soda break down into a powdery mess.

Also, superglue should be kept away from plastic that you'd want to keep pristine. The fumes could make the surface foggy. Great for gluing things you're going to paint anyway though.

In what ratio? Can you tell me more about its properties after curing? Thank you!

So you need to do multiple layers and build up the part gradually. Assuming you start with a broken plastic piece, use a good fixture to hold the part, and consider using a superglue activator spray on the plastic first. Then add as much superglue you can without dripping, and quickly sprinkle enough baking soda to saturate the super glue. Let it dry for a couple of minutes, dust off excess baking soda. Then alternate super glue layer, baking soda layer until you get slightly bigger than final shape. Let it cure fully and then sand it down.

I've seen people mend hockey stick blades with it, so it can definitely hold up to a beating. It seems to be a little elastic, so lasts well as long as the bond to the underlying material is good.

  > superglue activator spray

I had no idea this even existed. I typically lightly sand pieces.

Thank you.

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