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31.3 How do I make a Lava Lamp?




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This article is from the Chemistry FAQ, by Bruce Hamilton B.Hamilton@irl.cri.nz with numerous contributions by others.

31.3 How do I make a Lava Lamp?

Contributed by: Jim Webb <jnw4347@email.unc.edu>

Method 1. A new, easy, simple, cheap lava lamp recipe

Use mineral oil as the lava. Use 90% isopropyl alcohol (which most
drugstores can easily order) and 70% isopropyl alcohol (grocery-store
rubbing alcohol) for the other ingredient. In 90% alcohol the mineral oil
will sink to the bottom; slowly add the 70% alcohol (gently mixing all
the while; take your time) until the oil seems lighter and is about to
"jump" off the bottom. Use the two alcohols to adjust the responsiveness
of the "lava."

This mixture is placed in a closed container (the "lava lamp shape" is
not required, although something fairly tall is good) and situated over a
40-watt bulb. If the "lava" tends to collect at the top, try putting a
dimmer on the bulb, or a fan at the top of the container.

To dye the lava, use an oil-based dye like artists' oil paints or a
chopped-up sharpie marker. To dye the liquid around it, use food
coloring.

Two suggestions for better performance: 1) Agitation will tend to make
the mineral oil form small bubbles unlike the large blobs we're all used
to. The addition of a hydrophobic solvent to the mixture will help the
lava coalesce. Turpentine and other paint solvents work well. To make
sure what you use is hydrophobic, put some on your hand (if it's so toxic
you can't put it on your hand, do you want to put it in a container that
could break all over your room/desk/office?) and run a little water on
it. If the water beads, it should work fine. 2) For faster warm-up time,
add some antifreeze or (I've not tried it) liquid soap. Too much will
cloud the alcohol. Keep in mind that the addition of these chemicals may
necessitate your readjusting the 90% to 70% alcohol mixture.

Method 2. The "official" way - from a patent [3].

The patent itself is not very specific as to proportions of ingredients.
The solid component (i.e., the waxy-looking stuff that bubbles) is said
to consist of "a mineral oil such as Ondina 17 (R.T.M.) with a light
paraffin, carbon tetrachloride, a dye and paraffin wax."

The medium this waxy stuff moves in is roughly 70/30% (by volume) water
and a liquid which will raise the coefficient of cubic thermal expansion,
and generally make the whole thing work better. The patent recommends
propylene glycol for this; however, glycerol, ethylene glycol, and
polyethylene glycol (aka PEG) are also mentioned as being sufficient.

This mixture is placed in a closed container (the "lava lamp shape" is
not required, although something fairly tall is good) and situated over a
40-watt bulb. If the "lava" tends to collect at the top, try putting a
dimmer on the bulb, or a fan at the top of the container.

Method 3. The "less official" way - from Popular Electronics [4].

Several non-water-soluble chemicals fall under the category of being
"just a little bit heavier" than water, and are still viscous enough to
form bubbles, not be terribly poisonous, and have a great enough
coefficient of expansion. Among them: Benzyl alcohol (Specific Gravity
1.043 g/cm3), Cinnamyl Alcohol (SG 1.04), Diethyl phthalate (SG 1.121)
and Ethyl Salicylate (SG 1.13). [The specific gravity of distilled water
is 1.000.]

Hubscher recommends using Benzyl Alcohol, which is used in the
manufacture of perfume and (in one of its forms) as a food additive. It can
be obtained from chemical or laboratory supply houses (check your yellow
pages); the cheapest I could find it for was $25 for 500 ml (probably 2,
maybe 3 regular-sized lava lamps' worth). An oil-soluble dye is nice to
color the "lava"; Hubscher soaked the benzyl in a chopped up red felt-tip
pen and said it worked great. [Benzyl alcohol is "relatively harmless",
but don't drink it, and avoid touching & breathing it.]

Hubscher found that the benzyl and the water alone didn't do much, so he
raised the specific gravity of the water a little bit by adding table
salt. A 4.8% salt solution (put 48 grams of salt in a container and fill
it up to one liter with water) has a specific gravity of about 1.032,
closer to benzyl's 1.043. I find that the salt tends to cloud the water a
bit.. you might want to experiment with other additives. (Antifreeze?
Vinegar?)

This is put into a closed container and placed above a 40-watt bulb, as
above. Either way, I would suggest using distilled water and consider
sterilising the container by immersing it in boiling water for a few
minutes.. algae growing in lava lamps is not very hip.

Caveat: Some of these chemicals are not good for you. Caveat 2: Some of
these companies are not good for you if they find you've been infringing
on their patent rights and trying to sell your new line of "magma
lights." Be careful.

 

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