# Making Homemade Gobos With Acid



## 030366 (May 20, 2009)

I'd been cutting some gobos out by hand, and someone suggested that I could make a neater gobo using the acid bath method.

Has anyone here ever actually done this? How did it turn out?


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## Footer (May 20, 2009)

I have done it before, and it does work. Its a real pain to do however, not something I feel is totally worth it in my opinion. I will not tell you how to do it here, or what chemicals to use because it is a bit beyond our TOS. I would however go talk to an electrical engineer/technician about how they etch circuit boards, its a similar process.


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## jml42691 (May 20, 2009)

I have never done it personally, but we had a guy at my high school who used to do this himself at home, I am not sure how he went about doing this, but the end result was fantastic, he has since graduated, but some of the patterns he made were amazing and I used them myself this year.


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## Kelite (May 20, 2009)

Obviously acid etching gobos is possible at home, but there are hazards associated with the acid. (As if you didn't already know.) Be prepared to wear PPE and keep the fans running so you don't acid etch your bronchial tubes as well. 

The real question I'll ask is- how are you going to responsibly dispose of the spent acid? Our costs to ship buffered etchant back to the supplier often cost 2-3x more than the initial purchase of the stuff in the first place.


This is the main reason Apollo went to laser ablation for both glass and steel. Spent etchants have strict rules and policies associated with their use, so please be careful. If you choose to use an acid etch process on your own rather than working with a PCB maker, please consider how to responsibly dispose of this hazardous waste.


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## gafftaper (May 20, 2009)

You could but why would you want to? The cost of buying stock gobos is so cheap at around $10-$12. Why would you want to deal with hazardous chemicals? How much do the chemicals cost to buy and dispose of? What is your time worth? If you are doing lots of custom gobos, get yourself a Rosco Image Pro or buy a Selecon setup for transparency projection. Other than that just buy stock gobos. You might save a few bucks but doing it yourself is never as nice looking or safe. 

and if your problem is they don't make a gobo that looks like what you want. Submit your design to Apollo and they just might make it.


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## quarterfront (May 20, 2009)

gafftaper said:


> if your problem is they don't make a gobo that looks like what you want. Submit your design to Apollo and they just might make it.




They, in fact, WILL make it. It's about $60 for the first one and then a bit less for each duplicate, IIRC.

Back in the dark ages, before you could just Photoshop your gobo up and email it off to Rosco/Apollo/Gobos-R-Us, I did some acid bath etching. I was rarely happy with the results. The process was balky, and moreover it was messy enough that I never could justify going to the trouble of refining it, particularly with regard to the ratio of water to acid in the etching bath.

Now, the acid I was using wasn't a professional etching compound, it was just hardware store stuff. I won't bother naming the acid I used because I think you should choose not to bother attempting to do this process, but to satisfy any curiosity you might have, and to convince you that this is a boondoggle....

The basic procedure was to get old aluminium printers plate, sand any coating off of both sides, draw your design on the plate with pencil or fine point sharpie or whatever, then coat the entire sheet with clear acrylic spray paint. Next, you'd take an exacto knife and cut your pattern through the acrylic. Finally, you'd immerse the plate in a bath of acid and water and let it burn through the metal where you'd cut the acrylic layer.

The big problem was that if the acid was too strong (or the plate was too thick) the acid would etch sideways under the paint, not just straight through the metal. So the lines wouldn't be nice and sharp, they'd have pits and bumps and such. And, the paint had a tendency to peel up off the metal if you didn't prep everything just so, or maybe even if you did.

But the biggest problems, and these are substantial, have been mentioned above in this thread: 1) You're working with nasty toxic stuff, and 2) what do you do with the used acid? The fumes coming off the bath were definitely in the "DON'T INHALE ANY OF THIS EVER" category, and when you're done with the stuff you can't just dump it down the drain. You don't want to spill it on yourself, you don't want to spill it on your kid brother, you don't want to spill it on anything, which begs the question, "Where do I dump this out?".

What I'm trying to communicate is this: Back in the day, before commercial custom gobo fabrication was a matter of 20 minutes in PhotoShop, one email and a small fee, as a young and intrepid LD I felt pretty darn proud of myself that I could burn a mediocre gobo on the concrete slab outside my garage. It was slick and clever and I felt like a cowboy. Woo woo. But at the end of the day, the gobos I made sucked, even by the standards of that time; and the process of producing those lousy gobos that sucked was dirty, hazardous to my health and environmentally irresponsible. 

Stick with cutting foil cookie sheets with an exacto or move up to having gobos etched by a shop like Apollo that's set up to handle the process safely and cleanly. The "etch it yourself" option is a really lousy in-between kludge option that you should kybosh.


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## Kelite (May 20, 2009)

quarterfront said:


> Stick with cutting foil cookie sheets with an exacto or move up to having gobos etched by a shop like Apollo that's set up to handle the process safely and cleanly.



Our out-dated etching process has graduated to laser ablation, and the environmental repercussions of disposal was just one (albeit an important) reason in choosing to do so.


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## Footer (May 20, 2009)

You could always just buy a Versa Laser. For 4k you could make all the gobos you want.


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## Grog12 (May 20, 2009)

Or (and you all will be surprised about me putting this one out there) print off your gobo's on heat resistant transparencies and throw them into a Selecon.


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## awhaley (May 20, 2009)

My random wondering about this topic:

If a person were working with thin enough material, and were actually set up to do acid etching well (as in, had home-etched circuit boards before and knew what chemicals to go with and how to use and dispose of them safely...) do you think the toner transfer method that's so popular for pcb etching could be put to use for gobo printing? As in, print the gobo, photo copy it, then iron it onto the metal and dump this into the etchant? If you got the chemicals and material choice right this could improve the resolution and controllability to the point that you could actually photoshop an image and etch something worth putting in a light... perhaps.

For the pro world, or for one or two gobos, I'm quite certain the cost of setup, time, effort and reliability issues make this a ridiculous proposition compared to just ordering them from Apollo... but as a cool project in a college class... if you work out the safety issues it could be fun and give the students a chance to play with light in a creative and hands-on way.

If anyone is actually set up to safely play with this idea, I'd love to hear how it turns out! 

Art Whaley
Art Whaley Design


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## TimMiller (May 21, 2009)

um... i have an acid bath setup at my house and a water jet at the shop, but i much rather perfer to just send out an image to apollo or rosco and know it will be right the first time and they both do an incredible job, especially with laser cutting i have seen some metal gobos that appear to be glass due to the high resolution.


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## Footer (May 21, 2009)

awhaley said:


> My random wondering about this topic:
> 
> If a person were working with thin enough material, and were actually set up to do acid etching well (as in, had home-etched circuit boards before and knew what chemicals to go with and how to use and dispose of them safely...) do you think the toner transfer method that's so popular for pcb etching could be put to use for gobo printing? As in, print the gobo, photo copy it, then iron it onto the metal and dump this into the etchant? If you got the chemicals and material choice right this could improve the resolution and controllability to the point that you could actually photoshop an image and etch something worth putting in a light... perhaps.
> 
> ...



SIUE does this. Its one of their "things". For a long time they took a workshop to the Illinois High School Theatre Festival where you could make your own custom gobos and they would walk through the entire process. After doing it for awhile, they actually got pretty good at making them. I still have a few laying around that I did during a summerstock season there.


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## NickJones (May 21, 2009)

Ive said it before, and I'll say it again. Selecon Pacific.
Nick


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