# Photo Etching / Photo Milling of Gold sheet



## Goldartist (Sep 27, 2012)

has anybody tried photo etching / photo milling of gold sheet before?
I have a little knowledge about aqua regia and photoresist but am not sure how to do that both sides of gold sheet to cut the gold design 
if you know any company who make machine or if someone has tried this DIY please share
thanks in advance


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## etack (Sep 27, 2012)

I just scraped a table top CNC that did that on cooper. 

https://www.google.com/search?q=table+top+CNC+for+etching&hl=en&prmd=imvns&tbm=isch&tbo=u&source=univ&sa=X&ei=YGhkUNOJOcfGrQHdtoCgAw&ved=0CGEQsAQ&biw=1600&bih=785

the one I scraped was "homemade" in the shop. I still have the actuator from it. that I need to put on the ebay someday.

Eric


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## Goldartist (Oct 2, 2012)

Thanks
Has anyone tried of etching or cutting gold using aqua regia through photo etching process..


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## etack (Oct 2, 2012)

If you want to just etch the gold sheet chemically I would use a softer approach like HCl+bleach, or H2O2+ bleach, or even HCl+ H2O2. if you want to leave it in for a longer time.

If you were to use AR it would need to be pretty weak so it dosent eat though the gould to fast. If your ar was hot and you dipped it in for a given amount of time then dipped it in water after this may work. Just some thinking out loud I have never done this it should be relatively easy to work out the bugs, but it won't be cheap. good news is that the etched off gold will be there to get back out of solution.

It should work with AR you get a real nice leaf/crystal pattern.

I would also need to be above 18K for the acid to attack the gold. 24K would be the most predictable.

Looks like I need to get some 24K sheet to try this. 8) 

Eric


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## Goldartist (Oct 10, 2012)

etack said:


> If you want to just etch the gold sheet chemically I would use a softer approach like HCl+bleach, or H2O2+ bleach, or even HCl+ H2O2. if you want to leave it in for a longer time.
> 
> If you were to use AR it would need to be pretty weak so it dosent eat though the gould to fast. If your ar was hot and you dipped it in for a given amount of time then dipped it in water after this may work. Just some thinking out loud I have never done this it should be relatively easy to work out the bugs, but it won't be cheap. good news is that the etched off gold will be there to get back out of solution.
> 
> ...


Thanks Eric,
now good news I have 24 kt sheet with me for trial, now I need help how to bring back the dissolved gold in Aqua regia , do you know the percentage which am going to loose...


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## etack (Oct 10, 2012)

It all depends on how long you keep it in solution. The longer the more is eaten away.

Are you masking the sheet and then dipping it in AR. What is your plan?

Eric

This is my actuator on ebay to make a CNC engraver with.

http://www.ebay.com/itm/230860902756?ssPageName=STRK:MESELX:IT&_trksid=p3984.m1555.l2649


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## rickbb (Jan 23, 2015)

As a former printer with some experience in acid etching printing plates, (copper, zinc, synthetic rubber and even a few litho stones), I can tell you that you are in for a bumpy ride.

The process is more art than science and you want to try it on the most expensive substrate known. I hope you have more than one sheet to learn on, and you will need to learn how to retrieve the etched gold out of the solution. (Which is a whole different learning curve.)

Having said all that, I do believe that it can work, it will require some trial and error to get the correct method down though.

You mentioned two sided sheet, do you mean you want to etch all the way through like a piercing? Or just a slight surface etch to put a design on the sheet?

You will need to experiment with different dilutions of whichever acid mix you want to use. You may want to get some gold leaf, like is used in signage and lettering and practice with those to find the right mixture of acid that will etch at the speed you need so you can control the depth.

PLEASE NOTE, getting gold to dissolve/etch will generate poison gasses and vapors. You must do this in a separate building from where people are, under a fume hood or outside in a well ventilated area away from people, pets and anything you don't want to get very sick or die.


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## Lou (Jan 23, 2015)

Depends on how much attack you want on the gold.

I used to etch gold and other metal surfaces for various applications.

KI/I2 is a good etchant that I have used. It's important the proper mask is used.

My advice would be to read some of the literature from the semiconductor industry...
http://www.cleanroom.byu.edu/wet_etch.phtml

gold leaf is probably way too thin--it's at the borderline of what people can handle with bare hands anyway.

You shouldn't lose much if any gold if you save the etchant liquid for recovery, usually (if you can spare the quid) after it stops working.

Lou


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## goldsilverpro (Jan 23, 2015)

I know that iodine/potassium iodide etchants are used to etch gold in the electronics industry. This patent, 3957505, describes it quite well and, as patents go, it is quite instructive. This etchant is expensive but a way to re-generate the chemical is covered in the patent. The assignee of the patent, Bayside Refining, was owned at the time by a man that later became my partner in a silver refining venture in San Jose.

https://docs.google.com/viewer?url=patentimages.storage.googleapis.com/pdfs/US3957505.pdf

Sorry, Lou. I wrote this before I saw your post. 

As I am a 25 year user of gold leaf on signs, I would certainly agree with you about how fragile it is. Just to move a sheet from one place to another without tearing it requires a lot of experience. To etch a pattern, a mask (usually photoresist) must be attached to the gold. Unless the gold leaf was first completely secured, with no wrinkles (not easy), to a flat substrate with gold size, etc., there's no way a mask could be applied without ripping up the leaf. Even securing it might not work. Gold leaf averages about .0000035" thick. If you secure a sheet to a glass window, you can dimly see through it. If you carefully ball up a standard 3.375" x 3.375" sheet between your finger and thumb, the resulting ball is like a flyspeck. Sometimes you can't even find the ball, it's so tiny. A sheet weighs about .012g - 12g/1000 sheets. So called "double thick" is about 15g/1000.


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## rickbb (Jan 23, 2015)

Lou said:


> Depends on how much attack you want on the gold.



That is the $64,000 question. With printing plates we etched from 1/32" to 1/16" deep on copper plates and litho stones used in "engraving" type of printing. 

But on the zinc and synthetic rubber we would etch as deep as 1/4", depending on the type of press used.

Later DuPont invented a solvent based method for a new synthetic rubber that put all those acid etching guys out of work.


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## g_axelsson (Jan 24, 2015)

An old thread reawakened... by a new member posting it only two minutes after becoming a member. The link goes directly to a company doing etching in various metals, interesting but not related to precious metal refining. I would call the post made by leeweston1980 as spam, especially since he seems to be deeply involved in the company as a quick google search revealed.
The official youtube channel for the company is handled by leeweston1980!

I'm going to mark it as spam and letting the moderators decide what to do.

By the way the original poster, Goldartist, haven't visited the forum since late 2012.

Göran


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## Harold_V (Jan 25, 2015)

g_axelsson said:


> An old thread reawakened... by a new member posting it only two minutes after becoming a member.



He was rewarded by being banned and his useless post deleted. 

Harold


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## rickbb (Jan 25, 2015)

I need to start paying more attention to that type of thing before I post.


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