This years decoration

[novocaine]

Every year for the 8 years ive made my wife a christmas decoration. Never anything big or fancy. Just a little thingy. this year it was this.

 

[Mike G]

Well that's nice. Very artistic.

 

[AndyP]

I think you need to tell us more. What is it and how was it made?

 

[Chris101]

Yep, Very smart and a very cool Christmas Tradition to boot. Acid etch? Have you discovered an easy blanking method!?! Details, we need details!

 

[novocaine]

Its a 5mm chunk of aircraft grade (i chucked it in the air) aluminium. It wad made by electro etching in salt water. The tree was drawn and scanned in to a pc before being edited and smoothed etc. A resist was cut and stuck to the surface. It was cut round with a scroll saw before being cleaned up on the belt linisher. It was attached to the positive of a battery charger with a chunk of steel as the cathode on the negative. It took a bath with about 500ma at 5v for 10 minutes. It got polished and a hole drilled in it. The end.

I have a vinyl cutter. I dont do acid etching.

 

[Craig Salisbury]

very nice! I wish i had a star on my tree

 

[Chris101]

Thanks for the explanation, I did a bit of acid etching on some steel with mixed results. (Carp results but interestingstuff as an experiment), it would be nice to nail a method reliably.

 

[novocaine]

Thanks for the explanation, I did a bit of acid etching on some steel with mixed results. (Carp results but interestingstuff as an experiment), it would be nice to nail a method reliably.

the issue with acid etching it's really easy to get wrong as there as so many variables outside of your control that can screw it up.

for electro etching, even if they are out of your control they can't really destroy the outcome and if it does all go wrong you aren't tipping some fairly nasty chemicals over your hands.

there aren't many metals that it won't etch either as it's basically forced corrosion. if it's something small I'll often do it with a 9v battery (so no potential to burn the house down), you are basically shorting out what ever you use as a power source (so no lithium please), my car battery charger doesn't like it. a benchtop power supply is ideal but I haven't got one of those anymore.

a bit more info for you Chris.
plastic tub (I like takeaway trays for this). fill it with tap water. add salt and stir. add more salt and stir, add more salt and stir, go back a read these instructions to make sure you read it right, add more salt and stir. when the salt stops dissolving your about right. you now have a saturated brine electrolyte.
apply you mask, I use vinyl because I have it (and access to a cutter these days but that wasn't always the case) to a clean piece of metal. anywhere that isn't covered will be etched. tape a length of copper wire to the back of the piece then make sure it's completely covered except where you want to etch.
take a chunk of steel and do the same thing but without the mask. I've got a 2" square plate with a copper wire soldered to it already.

dump the thing to be etched in the water with the wire hanging over the side. if it's to big to stand up in the water, lay it in the bottom.
make a little set of rests from wire that sit about 1" above the piece. lay the steel plate on the rests so it is about 1" in front or above the work and send the wire over a different side to the work wire.

hook the positive of your power source to the work (anode)
hook the negative to the steel plate (cathode)
apply power, watch the bubbles. do not do this with an ignition source hanging over the top of the "bath" the bubbles are hydrogen and oxygen that you've "liberated" from the water, we done, bottle it and you can run you car on it (for about 1/10 of a second with the amount you are making).
leave it there for 5 minutes then check on progress. it will be quicker on steel/copper/brass than on aluminium as it forms a protective oxide. if it's deep enough, your done. if it isn't, put it back in.

I made my own branding iron from steel a few years ago this way, which says how deep you can etch without excessive undercut (about 1mm) if you get to deep it starts to undercut and can lead to loss of fidelity, this is controlled somewhat (unlike acid) as the cathode is directly in front so will corrode sides not facing it slower.

hope that helps.

 

[Chris101]

Thanks Dave. That is really helpful. It's not a major priority by a stretch but the little interesting projects are always a plus!

 

[ScaredyCat]

Great ide but my wife makes those in this house.

I do, however, look forward to Frank Howarth's Christmas ornament each year.

https://www.youtube.com/watch?v=bpjlY5L-d_8

 

[Phil]

Nice idea and good explanation, thank you.

I have tried scrollsawing small stuff like that, but it ends up as a mess (the scrollsaw has a mind of its own )

 

[novocaine]

update for this years decoration.

I posted this on Phils tree thread, but I'm worried I'll not be able to find it next year.