View Full Version : A difficult job/question?

Rodne Gold
02-10-2009, 4:52 AM
We have been asked to make a display item which has a see thru cavity that is filled with liquid.
Making the item is no problem , however the liquid therein has to seperate out into 4 discrete bands , each of which has a unique colour.
2 bands is easy , oil and water , but 4 is a mission.
We have tried mixing gearbox oil and low viscosity car oil , but they do not separate out , and if they did , it would take like an hour or more , the other issue is how does one colourize the oils.
We have suggested an option of filling the cavity with high viscosity oil and inserting 3 strips (its a rectangular cavity , looks like an oil barrel) of coloured perspex and then giving them a slight positive buoyancy so they gently float to the surface if the item is turned upside down and then righted ----

We were considering using water , castor oil , glycerine and normal gearbox oil as the 4 liquids , but i think the 2 oils and the water glycerine wont separate and once agian , colourants are an issue.

Anyone offer suggestions?

Mike Null
02-10-2009, 7:10 AM

Have you ever seen those multi-colored beverages they concoct at fancy bars? Don't know the contents but the colors separate until stirred.

James Stokes
02-10-2009, 8:02 AM
Is there any way to put a divider cap inbetween the colors? Or do the colors have to mix?

James Stokes
02-10-2009, 8:05 AM
Or how about jello.

Dan Hintz
02-10-2009, 8:49 AM
The problem with the drinks is they work on differences in specific gravity alone... shake them up and the alcohols never separate. The oil and water work on both specific gravity and the insolubility of the oil in water.

Try searching on multiple layer emulsions and hydrophilic / hydrophobic surfactants... you may come across a home-based experiment where someone found a good mix.

Rodne Gold
02-10-2009, 9:00 AM
Colours/fluids have to mix and then separate in a min or 2 - ie it has to do this whenever shaken and or turned upside down etc.
basically , its for an oil co , shell , and the colours represent the make up of the cost of a oint, so its basically 60% gold, 18% red, 10% blue and the rest a light gold or yellow. Qty is 500 units, 150mm high , 75 mm wide, 20mm thick, we charging at $20 a unit.

Steve Clarkson
02-10-2009, 9:16 AM
Don't forget vinegar......try mixing THAT with oil!

Also....how do you keep the liquid from leaking out of the award? Will weldon create a water-tight bond between two pieces of acrylic?

Dee Gallo
02-10-2009, 9:42 AM
I'm sorry I can't help here, but it never ceases to amaze me: the variety of problems and solutions that come up on the Creek. This is a true Brain Trust!

Martin Boekers
02-10-2009, 10:01 AM
Maybe a search through the site Instructables may have the answer.

Beware though it is a habit forming site. many unusual things there.
The other night I made carbonated fruit from instructions I found there.

Good reference site.


Scott Shepherd
02-10-2009, 10:37 AM
It's really simple, actually. It has to do with density. If you take 4 glasses of water, all different color and put different amounts of salt in them, they will have different densities and they will separate.

Really, come on, I thought everyone knew that.

Okay, now for the truth, I had no clue, went to Google and found this page- Might work, might not :) It might mess up when you shake it, I don't know.


bruce cain
02-10-2009, 11:06 AM
Maybe this might work?


Doug Griffith
02-10-2009, 11:55 AM
That is a tough one and could be one of those customer requests that just can't be done. At least not the way they want it. Even if you can find 4 fluids that separate, you still have to deal with coloring them - in the right order. A solution for a 3rd color could be a solid. something like sand. How about silicone? as in silicone brake fluid.

Good luck,

Rodne Gold
02-10-2009, 12:06 PM
Basically , its 15mm perspex , a rectangular block with a square hole in the middle , using silcon , we are sticking a 3mm clear full plate on front and back.
There is a front and back cladding of 1.2mm thick anodised aluminium etched with logos and lettering and these have a square hole so you can see the enclosure for the liquids , this all cladding hides the glue marks or silicon marks , the edge of the block is wrapped right round with anodised ally , so it looks like an ipod or whatever , the screen is the window with all the colours. The single saeam of the edge wrap is at the bottom.

What i have done is speak to the client and said that this colour banding is way beyond our expertise and field , but shell tech guys might have an answer re differing densities and colouring of oils etc , so let THEM call us. Otherwise im going with the "floaters" in a viscous oil , easy to stack em if we cut em in strips and they will always come up the right order etc.

Dan Hintz
02-10-2009, 2:15 PM
Maybe this might work?

Considering the toxicological properties of at least one of the fluids listed is unknown, I would suggest against this one ;)

The salt one is great for density demonstration purposes in a classroom, but it won't hold for more than an hour or two (unshaken) as the salt will eventually equalize.

Dyes have to also be immiscible between each fluid so they don't taint the color of the others... it may start out as 4 different colored layers, but after a few shakes it would be a muddy mess. Still layers, but each would have the same color.

Rodne, this isn't an easy problem and i think you're right to have the company take on the informational portion of the project. Two layers would have been a breeze, three a bear, but four is going to require some advanced knowledge of multiple chemicals and their interactions. Of course, they all have to be toxicologically inert for when they leak.

Margaret Turco
02-10-2009, 2:33 PM
I keep thinking of sealed clear pouches of liquid, but I'm not sure how to accomplish it.... Like a baggie of jello.

Shaddy Dedmore
02-10-2009, 2:51 PM
I used to have a framed thing, it had 2 sheets of glass that had about 1/8" between them, and a rubber gasket around them. There was a liquid, small amount of air, and 2 colors of sand. You'd mix it up and the sands would separate, different densities, if you did it right the air would trap the sand on the top half and the sand would slowly trickle down.

anyway... do the 4 layers have to be liquid? fine sand might work as one layer.


Dan Hintz
02-10-2009, 3:32 PM
I used to have a framed thing, it had 2 sheets of glass that had about 1/8" between them, and a rubber gasket around them. There was a liquid, small amount of air, and 2 colors of sand. You'd mix it up and the sands would separate, different densities, if you did it right the air would trap the sand on the top half and the sand would slowly trickle down.
I had one of those when I was a young'un... white and blue sand, I think the liquid was clear, and the container was oval shaped. I remember playing with that thing on and off for years, spending more time looking at the details as I grew older. First it was just a toy, then it was looking at the actual patterns created, then it was how the individual grains fell, then it was the chaos theory that controlled it all. Neat stuff.... thanks, Shaddy... I think I miss that toy!

Jack Harper
02-10-2009, 8:39 PM
Contact your local university and check with the chemistry professor. He will know or at least know who you should talk to for the answer. I often go to the local universities for the tougher questions. Most of the time they will help for the fun of it, although if it is involved I just hire them as a consultant.

Bruce Larson
02-10-2009, 10:20 PM
I would think that the Shell chemists should be able to solve that issue for you. Those folks deal daily with materials and their interactions.

Bill Cunningham
02-14-2009, 9:21 PM
Gasoline is lighter than both water and oil, Either gas or kerosene (you may know it as parafin) could be #3. you could probably colour clear kerosine

George D Gabert
02-15-2009, 10:51 AM
Could you use water, oil, sand, and some sort of floating media like foam beads.

These would seperate and would be able to be colored.


Bill Cunningham
02-15-2009, 4:24 PM
Have a look at this...

Its five, but four of them might be shake proof...
For some reason the main video won't play for me, but if you click 'advanced' it will load in a smaller window

Dan Hintz
02-15-2009, 4:42 PM
Its five, but four of them might be shake proof...
Nope... a few good shakes and it will become one with the universe. Honey, water, alcohol, dishwashing detergent, and oil.

Brett Carlson
02-16-2009, 12:40 AM
Ok, so we used to do a "floating screwdriver drink" It was Orange juice and Vodka, like normal, however, there was an extra step in this. Pour the OJ first, then take a paper towel and place it just above the oj, but not in the oj. Getting this right is the tricky part. After that pouring the vodka slowly on the paper towel allowed it to go through the paper towel and rest ontop of the oj, then removing the paper towel of course. A great shot because you would take in the vodka with a great oj chaser...I digress...So in your issue, I am thinking that you have to select liquids with enough of a different specific gravity to not mix, your oil and water is right, but to get four I am thinking of getting something with an alcohol base as a top layer, but this is tricky because after the object is moved, these things seem to break their tension barriers and mix anyway. Just a thought....now for that Vodka and OJ...

Andrea Weissenseel
02-16-2009, 5:07 AM
I remember way back in school we experimented with 3 layers

honey, water and oil - they separated again

I have no clou for the fourth though, maybe liquid wax ? Colouring water is easy, the oil you could get red with chili. But maybe food color works with all of them


Allan Wright
02-16-2009, 2:23 PM
If this is going to be moved around or set for a while, nothing that relies on just density will work as over time Brownian motion will mix the 2 differing density fluids together rendering the whole mixture uniform. Oil and water won't ever mix so they work. The problem is finding two more fluids that also won't mix. I can only think of one, and you won't be able to get a sufficient quantity of it without SERIOUS (justifiably so) legal hassles.

The third liquid I can think of is mercury. If you talk to a chemist they might be able to give you 4 liquids that are differing densities and not soluble with each other. Personally I think it's a nigh-impossible task due to the requirement of them to also separate rapidly which requires a high difference in densities.

Here's a thought. You're doing this work for an oil company. How about asking them to have their chemists work out the chemistry while they pay you to do what you do best - creating the laser-cut display?

Dan Hintz
02-16-2009, 6:19 PM
honey, water and oil - they separated again
Considering honey is little more than a sugar-water solution, the honey and water layers would eventually mix with enough shaking.

Ricardo Gomes
02-16-2009, 10:49 PM
don't forget that liquids cannot be corrosive. gasoline will probably burn the plexi, and it will lose it's "clearness"

this is indeed a tough challenge... :eek:

Scott Conners
02-16-2009, 11:30 PM
First thing that came to mind was glycerin-water-oil-alcohol, though I'm not sure about the separation speed of the alcohol and oil, as they are fairly similar in densities, depending on exactly which oil and alcohol are used. Naptha or another very light petroleum distillate might work better, but the exact type of plastic you are using will determine whether a blended petroleum solvent like naptha can be used.

This list might help you: http://www.simetric.co.uk/si_liquids.htm

Dan Hintz
02-17-2009, 12:17 PM
First thing that came to mind was glycerin-water-oil-alcohol...
Alcohol and water will mix immediately.

Bill Cunningham
02-17-2009, 10:35 PM
Alcohol and water will mix immediately.

I'll drink to that!

Scott Erwin
02-18-2009, 5:16 AM
I was thinking about your problem and it came to me that your customer should be able to suggest 4 fluids that would work. I then checked google for specific gravity liquids and found this tid-bit of information.


This may help you. I would guess you can look over the list, find items that are far enough in specific gravity and that are not soluable with the others on the list.

Jack, Bruce and Scott have said it best ....
and when you get your answer, it would be nice to know what you ended up with.....

Dan Hintz
04-22-2009, 2:02 PM

Curious how this one turned out...

Rodne Gold
04-22-2009, 4:44 PM
It never materialized...I think it was deemed impossible by all concerned.

Dave Fifield
04-22-2009, 5:40 PM
You could use CGI to do it....


Bill Cunningham
04-23-2009, 10:13 PM
Hmmm A hidef LCD with some fluid dynamics software.. Cool!