An 18-carat gold nugget made of plastic | Hacker News Reader

An 18-carat gold nugget made of plastic

ethz.ch

38 pointsLagogarda22 comments

I'm a bit puzzled that this is news.

The technique of using metal or stone powder with resins to create fake metal or stones is used since years.

When I was living in HK, in Sham Shui Po, I always wondered why there were these street stalls selling huge blocks of jade for cheap. Later a local friend told me it was just blocks of resin with embedded jade powder and other stuff. E.g. other stones ground up to simulate imperfections and dyes for the resin.

When used with metal powders to create sculptures, jewelry, etc. the technique is called 'cold casting'.

See e.g. https://www.youtube.com/watch?v=7VBVU3FNt-s

Ofc., people do this with gold too: https://www.reddit.com/r/ResinCasting/comments/bfiixq/cold_c...

The problem with all this is that these materials have plastic-like properties. The article mentions the sound the fake gold nugget make when hitting a surface sounding like plastic. This is one of the issues.

The weight is another one. Surface feel/texture depends on various factors.

The bottom line is: these materials look like the real thing but they don't feel/sound/behave like it.

It's 18k gold that weighs less than most 18k gold. So, if you want the look of 18k gold without the weight, this is one way of getting it.

I don't know how novel it is, but that sounds like an interesting material for people who don't like current high end jewelry due to the weight, but still want the aesthetics.

> No one wants to wear a heavy watch on their wrist, even if it’s made of real gold. After a time, it becomes uncomfortable and annoying.

This is a huge assumption. Wine tastes better served in a heavier bottle. More weight objectively does something with value perception.

Yeah, this caught my attention too. I like my watch to be semi-heavy - I like to feel it's on my wrist. A huge part of watch-wearing community like heavier watches.

The author used huge generalization, probably based on his own preferences.

I can testify to this: I do like my watches to be with a solid weight. That is why I like substantial steel watches.

Automakers spend a lot of time and money making car doors give a reassuringly heavy “clunk” sound when closed because such heaviness indicates quality.

I’ve seen bars of metal affixed to the inside of many electronic devices to give the device the proper “heft.”

A much simpler approach is to alloy gold with titanium. The resulting alloy is stronger and less dense than pure gold. Carat weight is determined on a weight fraction and because titanium is low density, a relatively large volume of titanium can be alloyed with a small volume of gold and still have a high carat number.

One particular gold-titanium alloy is significantly harder than most steel.

https://phys.org/news/2016-07-lab-titanium-gold-alloy-harder...

Apple did something similar with their ceramic/gold composite watch - there's some good info here:

https://leancrew.com/all-this/2015/03/apple-gold/

Unsurprisingly, paying a huge premium for a watch with less gold in it wasn't very appealing to people. Interesting idea though.

> Lovers of [...] heavy jewellery will be thrilled.

Presumably not? Lovers of gold jewelry, who don't like the weight may be, however.

> The conventional mixture is usually three- quarters gold and one- quarter copper, with a density of about 15 g/cm3.

That’s not true for this new lightweight gold: its density is just 1.7 g/cm3. And nonetheless it is still 18- carat gold.

Imagine comparing jewelry that is all “18 carat”, but some of it has 10x less actual gold. Seems like there will be a lot of fraud happening during a period when customers are not yet aware that the minimum amount of gold in an 18 carat piece has been reduced 10x. People will just hear “18 carat” and assume it means the same thing it meant before.

I thought 18 carat just means 75% pure gold. If something has 10x less actual gold does that mean it is 1.8 carats?

It has 10x less mass, but is still 75% gold by mass.

It's effectively a gold aerogel that's been solidified to no longer be gelatinous.

18 carat means: weight * 0.75 = gold mass.

AFAICT, this has a smaller weight and thusly smaller gold mass, but the proportion (0.75) is constant.

What does this enable that wasn't possible with plating or electro forming?

It would probably look really nice on a laptop or smartphone. Doesn't sound cheap to make, though.

I'd love to compare hitting both real gold and plastic gold with various kinds of hard objects.

>radiation shielding

Can someone explain to me what the heck they mean by this?

It sounds like it can be used as a radiation shielding material. Similar to the lead filled vests they use for x-ray scans.

Yes but actually no.

Can you elaborate or are you just asking questions you know the answer to already?

No, it cannot be used like lead. Radiation shielding of high intensity photons (X-rays, gamma, ...) works by attenuation. Attenuation is (almost) purely a function of how much material you have in between and how dense it is.

You can block alpha with anything, beta with any metal surface. I'm wondering if it's purely just nonsense as I suspect or if there's some aspect I'm not considering. I mean it does work against beta, so it's useful in that you don't need an additional surface, but that's pretty stretching.

Reply on news.ycombinator.com