Ask MAKE is a monthly column where we answer your questions. Send your vexing conundrums on any aspect of making to email@example.com. If we don’t have the answer, we’ll scare up somebody who does.
Non-archival paper that has yellowed over time.
In the post November is Paper Month, Susan asks:
What makes paper archival … or how long will it last?
Paper in it’s normal state is naturally acidic, leading to eventual degradation. However, most paper made today is acid-free due to a couple of factors. The filler used in paper used to be China clay, whereas now it’s chalk, which naturally has a high pH, making the paper pH neutral. It’s also often treated with magnesium or calcium carbonate, giving the paper an alkaline surplus. This protects the paper from further acidification, such as from sulfur dioxide that occurs naturally in the air.
Acid-free paper has a projected lifespan of 500 to 1000 years, depending on quality. As grades of paper increase to “conservation grade”, the standards become stricter. Lignin levels are kept below 1% in archival paper (lignin causes paper to become yellow and brittle over time).
True archival grade paper is made from a different material altogether — cotton rag. Used in documents of exceptional legal or historic value, cotton is significantly more durable over time at a neutral pH when compared to paper made from wood pulp.
I hope this answers your question, and all are welcome to contribute to the comments with additional information.
Erik Hersman (@whiteafrican, TED fellow and blogger) took some great photos at Maker Faire Africa, some of which we posted last week.
Hersman’s slideshow covers the whole event and includes the gorgeous shot of the four teen girls and their smart urine powered generator that has been making the rounds on the internet.
This is the fourth Maker Faire Africa. This year the event took place in Lagos, Nigeria; 2011 was Cairo, Egypt; 2010 in Nairobi, Kenya; and the founding year 2009 in Accra, Ghana.
In 2012 there were almost 60 Maker Faires around the world, all sharing the same passion and showing the same respect for the innovation, resourcefulness and creativity of makers—no matter where they live.
Learn more about how you can bring Maker Faire to your community here.
OK, it’s probably more accurate to say “flame resistant” or “flame retardant” paper, because the flame does actually damage the paper, but it just blackens and won’t catch fire or burn on its own. The treatment couldn’t be simpler: soak the paper in a saturated solution of borax (sodium tetraborate decahydrate) in water, then let it dry. Alum (potassium aluminum sulfate hydrate) is also commonly used for this purpose, but not quite as easy to find. Borax is available at most grocery stores.
Thanks to Ron Tozier for sharing this video.
Hydrospan 100 is a special “englarging” casting resin that swells, on curing, to 160% of its cast size. Surface details are well-preserved.
Continuing our monthly materials themes for 2012, in October we’re featuring materials used in molding and casting. That’s a broad area, so in keeping with the spirit of the spooky season we’re focusing in mostly on non-metals—polymers and composites and stuff—of the type that are commonly used to cast costume parts and props. From plaster-of-Paris to platinum-catalyzed silicone rubber, if it can be poured into or around a mold, and then sets up to form a more-or-less solid part, it’s fair game!
As always, if you’ve got a hot link or a subject you’d especially like to see covered under this theme, don’t hesitate to let us know, below!
Acidithiobacillus ferrooxidans is a gram-negative bacterium that lives, in the natural world, in iron sulfide (aka “pyrite,” aka “fool’s gold) deposits, where it eats iron and sulfur and excretes sulfuric acid.
Now, a team of graduates, undergraduates, and post-docs at New York’s Columbia and Cooper Union universities is working to develop a genetically-modified strain of A. ferrooxidans that can be used in place of toxic bulk chemical reagents to selectively etch copper to make printed circuit boards:
By genetically altering the bacteria, we intend to install a light sensitive mechanism which will enable us to etch copper in a desired pattern, leaving a finished circuit board. Once a blank printed circuit board is placed in a thin layer of solid media, the bacteria will be applied onto the surface of the media and light will be focused on it in a desired pattern. The light sensitive mechanism in ferrooxidans would activate and self-destruct in the pathway of the light. In the end, the circuit board will be “etched” by the bacteria everywhere but the illuminated spots, leaving the desired pattern behind on the circuit board.
The combined Columbia-Cooper Union team are entering this project in the 2012 iGem Synthetic Biology competition. Check out the link, below, for more details, and come see them in person, if you can, at World Maker Faire 2012.
IGEM 2012 Team Information – Columbia-Cooper-NYC
Before anyone gets confused, please note that the purpose of a device like this is not to keep dangerous stuff inside from getting out, but to keep corrosive stuff outside from getting in. Specifically, it’s designed to protect air-sensitive organisms (or chemicals) from the highly corrosive sea of oxygen that envelops our world. In biochemistry, it’s sometimes called an “anaerobic chamber,” but an essentially identical device is also commonly employed in air-free chemistry technique, where it’s usually just called a “glove box.”
Vacuum metallization is a process for coating objects, most often engineering plastics, with an extremely thin (~0.1 μm) metallic coating. It’s done, essentially, by condensing vaporized metal fumes on the surface to be treated inside a vacuum chamber, and is a common means of “chrome plating” plastic parts used, for example, in toys.
I have been hacking on some cheap R/C cars, lately, and wanted to etch these metal films off of a few of the bits, A) to prevent it from shorting across exposed electrical connections and B) for aesthetic purposes. It looks gaudy, IMHO, and does not take paint very well. I knew that the usual strong acid and base suspects would remove it, and at first I was etching parts in disposable plastic cups containing about 12 oz of tapwater and 1/8 tsp Red Devil lye, which of course is sodium hydroxide. Hydrochloric (aka muriatic) acid will also do the trick.
I am not especially intimidated by these substances, but many people don’t keep them around, for whatever reasons. And unless you’re in a hurry, there’s no reason to use them if something milder will serve. I got curious, and did a simple test with some household chemicals. I broke a metalized “roll cage” from an R/C truck into five pieces and soaked each in a different solution overnight. I used vinegar, an arbitrary mixture of vinegar and hydrogen peroxide (the strong hair-bleaching kind), straight hydrogen peroxide, diet coke, and an arbitrary mixture of diet coke and hydrogen peroxide.
It was not a very scientific process, but vinegar seems to work well. Specifically, I used “extra strength” distilled white vinegar labelled as “9% acidity.” Hydrogen peroxide seems to have no useful effect. Diet coke works pretty well, but the carbonation causes bubbles that displace etchant and leave shiny spots on the surface. Your mileage may vary, depending on just how your parts were metalized (and with what metal), but if you have need of this process, vinegar may be a good place to start experimenting. Also, though I wanted to completely remove the metal films from my parts, it should be fairly straightforward to apply masking agents and etch decorative and/or functional patterns in them, if you should need or want to.
Chilled Cast Iron – Unknown Artist, via PAXCam
Metallography is a method of materials analysis used to characterize the microscopic structure of a metal sample. Generally, the process involves cutting a section from some object of interest, polishing its surface to high smoothness, and etching it with a chemical agent to highlight grain boundaries, inclusions, and other microstructural features. The sample is then imaged using one of a number of types of microscopy. The resulting pictures are often strikingly (if incidentally) beautiful. That’s OK by me, personally—incidental beauty is usually my favorite kind.
I have written here about metallography before. Back in 2009, I had a hard time finding nice high resolution metallographic images to share with you. Happily, there seems to be more of it available online, now, and I’ve picked out three academic and commercial image libraries, sampled above and linked below, for those interested in digging deeper. Some of the captioning is still less detailed than I like (many of PAXCam’s images, for instance, are simply labelled as “Metallurgy Image”), but beggars oughtn’t to be choosers. So I’ll simply leave it with this: Hey metallographers! More pretty pictures! Please and thank you!
CCWJ Pictures — Metallography
PAXCam Image Library — Metallurgy Images
Struers — Materialographic Wallpapers
As promised, here’s a tasting menu featuring some of my favorite metallurgical content from our archives, arranged as usual, in mysteriously-appealing (and entirely arbitrary) top-ten format. Narrowing it down to just ten involved some hard choices; this subject is rich, and we’ve covered it a lot. A second round-up, perhaps at the close of the month, may be in order. In the meantime, I’ve got a lot of cool stuff on my to-blog list, and it’s growing fast as your suggestions roll in. Thanks to everyone who’s already chimed in, and please do keep ’em coming. Metals month, though abbreviated, is shaping up to be a good one.
Solid Copper Rescue Tool
Showing Off Aluminum’s Natural Reactivity with Gallium Alloy
Mercury “Beating Heart” Works With Gallium, Too
Continuous casting copper disc (99.95% pure), macro etched, ∅ ≈83 mm, by Heinrich Pniok.
Well, what’s left of August is Metals Month, I should say. A broad subject, to be sure, and with only a couple of weeks to explore it, I want to be fairly strict about focusing on interesting and unusual metals themselves (and processes for working with them) rather than more general “cool stuff made from metal.” Even limiting the scope this way, our archives are rich with relevant content, and my first priority is to round up the best of it. Look for that tomorrow, and in the meantime, as always, if you have suggestions for subjects you’d like us to cover, under this banner, please let us know below.