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Old 04-15-2012, 03:49 PM
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bridog bridog is offline
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Questions about etching aluminum and copper plates

Hi everyone
haven't done a chemical etch in many years (that was zinc plate using nitric acid). I remember this was pretty nasty stuff and required us to wear heavy duty gloves, facemasks and have pretty strong vacuum type venting in the print lab. Just reading up about aluminum plate etching. Has anyone done any etching using this metal with chemical baths such as stannous chloride or ferric chloride? If so do you require ventilation like you would etching using nitric acid?
I understand these are safer alternatives but can't seem to get much info about the actual safety aspects of working with these particular chemicals.
Think I read you need to etch aluminum plate in ferric chloride by inverting the plate to face downward in the bath.
I am also curious about the alternatives to coat your plate with instead of asphaltum.
Lots to learn and I would like to know other's experiences with the newer materials and mordants.
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Last edited by bridog : 04-15-2012 at 03:51 PM.
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Old 04-16-2012, 03:00 AM
charlesgmorgan charlesgmorgan is offline
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Re: Questions about etching aluminum and copper plates

Quote:
Originally Posted by bridog
Hi everyone
haven't done a chemical etch in many years (that was zinc plate using nitric acid). I remember this was pretty nasty stuff and required us to wear heavy duty gloves, facemasks and have pretty strong vacuum type venting in the print lab. Just reading up about aluminum plate etching. Has anyone done any etching using this metal with chemical baths such as stannous chloride or ferric chloride? If so do you require ventilation like you would etching using nitric acid?
I understand these are safer alternatives but can't seem to get much info about the actual safety aspects of working with these particular chemicals.
Think I read you need to etch aluminum plate in ferric chloride by inverting the plate to face downward in the bath.
I am also curious about the alternatives to coat your plate with instead of asphaltum.
Lots to learn and I would like to know other's experiences with the newer materials and mordants.

I etch aluminum plate all the time. Stannous chloride and ferric chloride are both pretty nasty, and I would not use them. There is a very old technique (hundreds of years old) that is good for aluminum, zinc, and steel ... but does not work for copper. And it is about as low in toxicity as anything you will ever use.

You will need the following chemicals:

copper sulfate ... sometimes called blue stone ... used as an anti-fungal spray for fruit trees and as a foot bath for sheep and cattle to combat foot rot ... try a good garden store or a good farm supply store ... comes as coarse blue crystals

sodium bisulfate ... used to adjust the ph of swimming pools and hot tubs ... one brand is called PH Down ... buy it in pool supply stores or Walmart ... comes as a white powder.

table salt ... get the non-iodized variety from your local grocery

Mix these three together dry in a plastic container. Use a scoop, like a table spoon or coffee scoop to measure as follows:

copper sulfate ... .. 9 scoops
sodium bisulfate ... 2 scoops
table salt ............. 9 scoops

In other words, the proportions are 45% copper sulfate, 45% table salt, and 10% sodium bisulfate.

Make a concentrated solution of the mixed powders ... fill a glass or plastic jar with water and then add several scoops of the powder. Put a lid on the jar and shake the bejabbers out of it to dissolve all the powder. Repeat the process until you cannot dissolve any more of the powder. Your solution will be a lovely blue.

For a resist, I use shellac from the hardware store because it is cheap, pretty non-toxic, and it dries very quickly. I color it by cutting open a permanent red felt pen and putting the ink soaked felt directly into the shellac. That way you can see any gaps when you coat your plate. I have also used oil-base inks for a resist ... but they must have cobalt drier added or they take forever to dry. If the shellac needs to be thinned, use Denatured Alcohol from the hardware or paint store ... that is just ethanol that has a small amount of something noxious added to keep people from drinking it. Ethanol is grain alcohol .... booze ... and will not harm you if you get it on your skin. You could use 99% isopropyl alcohol from the drug store, but that is expensive. Avoid methanol, as it is carcinogenic.

For plates, I often get used aluminum off-set press plates from a local print shop for nothing. Or I buy rolls of aluminum flashing from a building supply store ... you can buy it in several widths by the foot. I use acetone based contact cement to glue the thin aluminum to plexiglass to give it some backing and make it easier to handle. Cut the aluminum with a guilotine paper cutter or score with an snap-off blade cutter and bend a few times to break it. Bevel the edges of the plexi-aluminum sandwich with a file and sandpaper or with an electric sander. Once the sandwich is made, use a palm sander to smooth the surface of the aluminum and remove any old ink or other material that may be on the surface. Start with 250 grit sandpaper, go to 400, then to 600, and even to 1200 if you want almost no plate tone. these high grit sandpapers should be available in automotive supply stores if your local hardware does not have them. Then just use a paint brush to coat the aluminum with your resist. You will not need to coat the back of the plate, as the plexiglass will not be affected by the mordant.

I have also used galvanized steel plate. You can find a shop that makes heating duct work in almost any city of any size. Or check with a machine shop. They should have a variety of steel plate available and can cut it to size for you. Or you can buy a larger sheet and cut it yourself with a power jig saw and metal cutting blade. Steel plate of 16 guage or so will not need any backing. Again, bevel the edges with a file. Then use a paint brush to coat both sides of the plate. Mild steel plate or galvanized steel plate will not need to have the surface sanded or polished, but you should clean it well to remove any oil or grease.

Needle your design through the resist as usual ... if you slightly warm the shellac you can get finer lines ... but be careful with your warming the aluminum/plexi plates or the plate will warp because the aluminum and the plexi expand at different rates.

To etch, just put the needled plate into the mordant bath. Aluminum will etch in 2 minutes or less; zinc plates take about 15 minutes; steel plates take about 30 minutes. You will see a brown sludge forming ... that is pure copper. The metal (aluminum, zinc, steel) goes into solution, and the copper from the copper sulfate precipitates out.

If etching steel, you will get a brownish scum on the surface of the solution. That is iron oxide and is very staining. You can pour the used mordant through a coffee filter to remove the scum. If etching aluminum, the solution will stay clear.

Wash your plate with water to check your etch. Return it to the bath for more etching if necessary. When done, you can use concentrated orange cleaner (from your hardware store or building supply store) to remove the shellac. You could use alcohol to remove the shellac, but it is very volatile and expensive. To remove an ink resist, I use acetone. Acetone is very volatile and highly flammable, so use it outside or with plenty of ventilation. Actone is not a neurotoxin (but just like alcohol, it will make you woozy if you inhale lots of it), it is not a mutagen, and it is not carcinogenic. It is produced naturally in the body and is eliminated from the body. So it does not accumulate in the body. It is MUCH safer than lacquer thinner, turpentine, and other solvents.

This mordant solution will not hurt your skin. It is not corrosive. It is not absorbed to any significant degree through your skin. It may stain your clothes if it gets on them, but it will not eat holes in your clothes. The only gas given off during the etch will be a small amount of hydrogen, which is of no concern. The solution is toxic if you drink it, so do not drink it and do not leave it where a kid might drink it. An adult would have to eat several ounces of copper sulfate to be fatal. Sodium bisulfate is about the same toxicity as table salt. If an adult were to eat a teacup or two of ordinary table salt it would be fatal. But we do not regard table salt as highly poisonous.

You can use the mordant over and over, but it will be depleted in time ... gets more of a greenish hue rather than the nice blue color. Store it in a well marked plastic container with a plastic lid. To dispose of it, just dilute it with water and pour it down the drain. Certainly in the amount you will be using, it poses no environmental danger ... no more than than spraying fruit trees or draining your hot tub or flushing your urine down the toilet.

Hope this helps.

Cheers ....... Charles
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Old 04-28-2012, 09:48 PM
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mooksii mooksii is offline
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Re: Questions about etching aluminum and copper plates

Hello Bridog

Wow! Great post Charles!

I use a similar recipe as Charles but I leave the sodium bisulfate out (- and using this mix on aluminium I get the brown scum and the solution becomes cloudy.)

I'm currently etching aluminium plates using 100grams salt 100 grams copper sulphate to one litre of water. I leave the plate in the solution (face up) for between 2 - 18 minutes depending on the depth/weight of line I am looking for.
When the plate is in the solution - don't wipe away the bubbles, that appear on the plate, as this is the etch in process. I also noticed that larger unsealed areas will darken sightly as the etch progresses!! ( the magic of printmaking!!!!)

I use a bitumen resist called 'brushable hydroseal' made by tremco. (I'm in Australia so not sure if it is available overseas.) This resist can be removed using turpentine.
I made 2 test plates with varying etch times from 0 up to 18 minutes using line and aquatint techniques for a guide for my printmaking - very helpful reference when determining how I want my print to look : )

Even tho this recipe is friendlier than nitric acid, I always etch outdoors as I read somewhere that chemicals are 1000 times more toxic when used indoors.
Better to be safe than sorry

Instead of using rosin for aquatinting I use normal spray paint - a quick, cheaper and easy aquatint alternative with very similar results.
NB: when using a spray paint try to press the nozzle gently and slowly to achieve the aquatint result.
Just spray it on and wait until it dries and its ready for etching! Less tedious than the rosin process.

I purchase my aluminium plates from a local metal supply store. They are nice enough to cut it to size for me : )

The rest of my process is the same as the one posted by Charles

How exciting to be etching again!!

Best wishes
Mooksii
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Old 04-29-2012, 09:38 AM
charlesgmorgan charlesgmorgan is offline
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Re: Questions about etching aluminum and copper plates

The sodium bisulfate will keep all of the aluminum sulfate in solution so that your mordant does not become cloudy and you will not get the scumming on the surface. The cloudiness in the mordant is a result of aluminum sulfate precipitation. That precipitate can build up in your lines and slow or stop the etching process.

That is a good suggestion about the test plate. How the etch progesses depends a great deal on the concentration of the solution. I use a very concentrated solution. If I left an aluminum plate in the mordant for 10 or 15 minutes, it would etch completely through the plate! I suspect at least part of the reason you etch so long may be the aluminum sulfate buildup clogging the lines.

As for aquatint, aluminum plate is self-aquatining. Just give it an open bite, and the plate will hold ink ... the open bite results in very small, randomly spaced pits. That is one of the beauties of aluminum plate etching. The darkness of the aquatint is a function of how long you leave the open bite ... longer = darker.

The gas bubbling off is just hydrogen ... hydrogen is not toxic, but in large quantities it could explode if ignited. There is not enough hydrogen being given off when etching a normal sized aluminum plate to be of any concern.

Turpentine is a known carcinogen, so I avoid it. So-called odorless paint thinner would be a safer alternative. If you have bio-diesel fuel available, that is also a good thing to try as it is very safe ... but it must be bio-diesel which is made from cooking oil, not regular diesel made from petroleum.

I apologize in advance ... I do not mean to sound like a know-it-all, nor to be critical. I am just making a few suggestions. We all develop our own ways of working, and whatever works for you is great.

Cheers ....... Charles

Last edited by charlesgmorgan : 04-29-2012 at 09:42 AM.
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Old 04-29-2012, 05:26 PM
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bridog bridog is offline
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Re: Questions about etching aluminum and copper plates

appreciate all the input to this query
no need to apologize Charles...think everyone has their own takes and experiences worth sharing and if they cross paths that is wonderful...if not then it is something learned for that individual that works for them...all tips and advice are most welcome!
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Old 05-17-2012, 12:23 AM
Preußischblau Preußischblau is offline
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Re: Questions about etching aluminum and copper plates

Has anyone ever tried any other substances for biting their plates (vinegar, coca-cola, other easy household things)? Info for copper would be ideal (since I have some of that), but I can get 36 gage aluminium quite easily. Longer biting in the bath is acceptable to me.

Or am I asking for crazy things?

I'm trying to find an apartment-able alternative to engraving, which is time-consuming and deliberate-looking, and generally not the best for the kind of sheep-wool texture I'm looking for.
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Old 05-17-2012, 04:22 AM
Red Dot Red Dot is offline
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Re: Questions about etching aluminum and copper plates

At Edinburgh Printmakers we use a very simple, non toxic ground called a BIG ground. It is available from its inventor (Andrew Baldwin) and also from Intaglio Printmakers in London. It is rolled on to the plate and can be used as either a hard or soft ground. For use as a hard ground it has to be heated on a hot plate or in the oven.

http://www.printmakingstudio.co.uk/i...67&It emid=30

http://intaglioprintmaker.com/

For zinc Copper Sulphate is used in the studio and for copper we use Ferric Chloride.

Here is a link to INKTERACTION's forum where there are a number of queries and responses on mordants. Alfons Bytautus was the etching 'guru' at Edinburgh Printmakers for many years and was mainly responsible for switching from traditional etching many years ago.

http://inkteraction.ning.com/forum/t...ide-for-use-in
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Old 05-17-2012, 04:44 AM
Red Dot Red Dot is offline
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Re: Questions about etching aluminum and copper plates

Additional points -

The BIG ground can be removed with Brasso or commercially available compounds - see link above for more info.

.....and I spelled Bytautas wrongly!
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Old 05-17-2012, 04:46 AM
Red Dot Red Dot is offline
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Re: Questions about etching aluminum and copper plates

....and another one! Andrew Baldwin uses icing sugar (not sure what that is in the USA) as an aquatint.
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Old 05-17-2012, 04:56 AM
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Diane Cutter Diane Cutter is offline
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Re: Questions about etching aluminum and copper plates

Icing sugar would most likely be what we call powdered sugar (main ingredient for making icing at home).

Diane
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Old 08-10-2012, 07:35 AM
Uncle Battuh Uncle Battuh is offline
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Re: Questions about etching aluminum and copper plates

Hello evrybody!!

Sorry bringing this topic back to life, but I'm having a little problem using the copper sulfate mordant: I wasn't able to find sodium bisulfate to add to the mix, so I simply went on with Copper Sulfate and non-ioded salt. It worked fine on the first etchings, but now my solution has become a greyish-green coloration, and it's losing its etching power, e.g. some lines that i cut in the ground don't even become engraved.

Problem is,here where I live (Curitiba, Brazil), there's no sodium bisulfate to be found. I searched at swimming pool supplies stores, but they don't even know the substance, as they use other products tho lower the ph.

Question is: is there any replacement to the sodium bisulfate to keep the mordant fresh and effective?

(sorry for the broken engrish)
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Old 08-11-2012, 01:52 AM
charlesgmorgan charlesgmorgan is offline
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Re: Questions about etching aluminum and copper plates

When your mordant takes on a greenish tone, that means it is pretty exhausted ... it has precipitated out most of the copper. At that point I just chuck it and mix up some more. The copper sulfate and table salt mordant exhausts fairly quickly, as compared to nitric acid.

The sodium bisulfate is there just to provide a very mild acidification. The acidification helps to keep the aluminum sulfate in solution so it does not gum up the etched lines. The main reaction is between the aluminum and the copper sulfate ... CuSO4 and Al. Essentially the Al goes into solution as AlSO4 and the Cu precipitates out. The process is a little more complicated than that, as there is some hydrogen gas released. The table salt is there to provide electrically charged ions to facilitate the reaction.

There are other acids you could use, although I hesitate to recommend them. For example, a very small amount of battery acid (sulfuric acid) would do it ... H2SO4. But that is nasty stuff, and I have no idea how much would be required. It is possible that the other compounds used in your area to lower the ph of hot tubs would also work. See if you can find out the chemical name of the active ingredient and pass it along. Here in Canada (and in the US) companies are required to file a Material Safety Data Sheet, listing all noxious compounds in their products. Locally the trade name of the stuff is Ph Down. If I do a Google search on "MSDS Ph Down", I will get links to the MSDS for the product and that will tell me it contains sodium bisulfate. If there is some similar requirement where you live, then perhaps you can use Google and the trade name of the local hot tub product to find out what it is. If it were me, I would just give the stuff a try anyway and see if it works.

Cheers ..... Charles

Last edited by charlesgmorgan : 08-11-2012 at 01:54 AM.
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Old 10-08-2012, 12:53 AM
TimKelly TimKelly is offline
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Re: Questions about etching aluminum and copper plates

Mooksii,
I am based in Sydney. Can you nominate any particular spray paint brand available in Australia. By the way this string of posts regarding etching aluminimum is the most through source of information I have read to date on this subject. It has been very helpful. Now I am off to the local hardware store to get wet and dry paper.
Thanks.. Tim
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Old 02-25-2013, 01:57 PM
mymdb mymdb is offline
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Question Re: Questions about etching aluminum and copper plates

Thank you guys for the great information in this thread. I'm using the copper sulfate bath mentioned here by charlesgmorgan to etch aluminum. Any recommendations for a screen printable resist?
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Old 08-08-2013, 01:59 PM
feckless feckless is offline
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Re: Questions about etching aluminum and copper plates

Great thread! I realize this is an older thread, but it still seems to be alive. As far as screen printable resists, I'm wondering if you've tested any of the normal screen printing inks (assuming they can be removed with acetone once dry on metal ). I have etched aluminum on a small jewelry scale using resists such as Sharpie paint pens (paint pen, not the marker), masking film, StazOn ink (used a lot in craft stamping)... and all of these have worked excellently -- which is why I'm thinking that your screen printing inks might work just as well as long as they can be removed post-etch.
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