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We've got lots of new content in the Make: Science Room, including a whole new Forensics series on the many methods of fingerprinting. Tired of those bitter family disputes over who ate the last ice cream sandwich? Take the wrapper to the lab and find out for sure!
We also have a lab on testing for lead paint and an introduction and series of labs on colloids and suspensions. What in blue-blazes is a colloid, you ask? Why it's a "two-phase heterogeneous mixture made up of a dispersed phase of tiny particles that are distributed evenly within a continuous phase." Think: homogenized milk. It has tiny particles of liquid butterfat (the dispersed part) suspended in water (the continuous part). That's a colloid.
And then there are sols, that's a "solid phase dispersed in a liquid continuous phase. Ordinarily, a sol is a liquid, but it can be converted to a semi-solid gel by adding a gelling agent. In some cases, the solid phase itself may also serve as the gelling agent."
An example of a gelled sol is the notorious Super Napalm B. And guess what? We show you how to make it -- just in time for Halloween. We're kidding. KIDDING! This is serious stuff, a cool experiment, but one with real dangers. This is seriously volatile burning material that's also a seriously sticky gel, a deadly combination (hence the notoriety).
Here's the door to the Science Room >>
In the Maker Shed
And don't forget all of the awesome science-related products now carried in the Maker Shed, including a Latent Finger Printing Kit and a Lead Paint Test Kit (seen above).
That's odd, I just said to myself "let's see if there's anything new on the MAKE: Blog before I start shopping for lead testing kits"! How's that for a coincidence?
Anyhow, how well would this kit work for detecting lead in something not paint-related? Say, chunks of metal of unknown composition and origin? Could the reagents be swabbed onto a test area and used that way, perhaps? God only knows what the brass and other materials I use in my projects actually contains, and I'd like to start testing for at least one toxic element...
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Hi, Jake
Excellent question. The short answer is that you can use this kit to test metals, ceramic glazes, and other potential lead-containing materials around the house.
Paint is the easiest to test, because lead-based paints usually (not always) use lead carbonate. That compound is extremely insoluble in water, but reacts readily with acetic acid (vinegar) to form very soluble lead acetate. All you need to do to test a paint sample is abrade the surface or peel off a small chip, put it briefly into contact with a small amount of acetic acid, and test the extract.
Metals and glazes are a bit more difficult to test because the lead isn't as readily accessible to the acetic acid extraction reagent. In, for example, a pewter plate, the lead is present as lead metal (alloyed or mixed with other metals) rather than as lead carbonate. The acetic acid will still react with lead, even in metallic form, but it takes longer. IIRC, the government standard for testing dinnerware, toys, and similar items requires putting the item into contact with a specified volume of 5% acetic acid and allowing the reaction to continue for 24 hours.
The kit contains 25 mL of glacial (99%+) acetic acid, which is diluted to 10% before use. That gives you 250 mL (just over 8 fluid ounces) of 10% acetic acid, which is enough to test 100 or more paint samples, but probably not enough for your purposes. If you have many (or large) samples to test, just pick up a gallon of distilled white vinegar at the supermarket or Costco. Distilled white vinegar is essentially pure 5% acetic acid, so it'll work fine as an extraction reagent. If your samples are too large to immerse in a practical amount of vinegar, you can use modeling clay or something similar to build a dam to contain the vinegar. Let the vinegar remain in contact with the object for 24 hours and then test the extract solution. If it's an art object or something similar, I'd recommend you try it first with a small amount of acetic acid on the bottom or another inconspicuous place.
If you have to test for just one toxic heavy metal, lead is definitely the one to test for. Cadmium, mercury, and other toxic heavy metals are much less common, particularly in objects or materials made during the last several decades. Lead, on the other hand, is so useful that it's still in wide use even in paints (not residential, but commercial and industrial paints are still permitted to contain lead, and many do).
Please keep us posted on your test results.
RBT
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