How to make a Lava Lamp

The following is taken from the sci.chem FAQ.

How does a Lava Lamp work?


Contributed by: Jim Webb 


A container filled with clear or dyed liquid contains a non-water-soluble 

substance (the "lava") that's just a little bit denser (heavier), and has 

a greater thermal coefficient of expansion, than the liquid around it. 

Thus, it settles to the bottom of the container. A heat source at the 

bottom of the container warms the substance, making it expand and become 

less dense than the liquid around it. Thus, it rises. As it moves away 

from the heat source, it cools, contracts a bit, and becomes (once again) 

heavier than the medium. Thus, it falls. Heavy, light, heavy, light. 

Sounds like a Milan Kundera novel. 

(Actually, to be more precise: dense, less dense, dense, less dense.)


How do I make a Lava Lamp?


Contributed by: Jim Webb 



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 US Patent # 3,570,156 March 16, 1971)



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,[3] )How to make a

Lava Lamp, by Ralph Hubscher, 

  _Popular Electronics_ magazine, March 1991, p. 31 (4). Gernsback 

  Publications.)



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 

sterilizing 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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