This is an excerpt from a really
great web site. Unfortunately, I dont have the link anymore and forgot where
it came from. Luckily I saved the text.
What I like about these recipes is they explain some of the science behind
the mixes.
Welcome to the fascinating world of non-Newtonian fluids! They get their name from the fact that they do not fit Newton's laws of how true liquids behave (specifically, in how they react to shearing forces). Quicksand, many pastes and glues, gelatin, and ketchup are all non-Newtonian fluids. There are two main types of non-Newtonian fluids, rheopectic and thixotropic. These slimes, oozes, globs and the rest are rheopectic, which means they show an increase in viscosity with time under a constantly applied stress. They resist flow dependent on the velocity of flow. If something acts on them with a small amount of force (if you stir them slowly, or let you fingers slowly sink into them) they won't offer as much resistance as they would if a greater force acted on them. If you punch a good stout ooze, it should resist about as much as a brick wall. They fight back. Thixotropic fluids, on the other hand, tend to become more viscous under low shear stress and less viscous under higher shear stress. Paints typically are thixotropic fluids; they flow easily when being brushed on, and stay put once applied.¹
Elmer's Slime
One of the simplest of the slimes, and a favorite among schoolteachers. Not
terribly toxic, but watch the kiddies so they don't eat it. It produces a
lovely, white (unless you color it), opaque goo. It will dry out, so store
it sealed and refrigerated (zip lock bags work well). It also has a limited
shelf life, and may eventually develop mold (horrors!) It (usually) cleans
up easily. If it dries on anything, try soaking in water. It is best not to
set it on wood, fabric, or any other surface that does not clean up easily.
This is the quick and easy method.
Materials
· Teaspoon (or metric measure)
· Big jar or measuring cup (1 qt. or 1l)
· Bowl - 2 quart (2l)
· Measuring cup
· Borax powder
· 4 ounce (120 ml) bottle of white glue (not school glue!)
· Water (pref. distilled)
· Food coloring (opt.)
Pour the glue into the jar. Fill the empty glue bottle with water, and add
to the jar. Stir. You can add food coloring here if you want to be festive
- a few drops will do. Pour one cup (240 ml) of distilled water into the bowl
and add 1 teaspoon (5ml) of borax powder. Muddle well. Slowly add the glue
mixture to the bowl, stirring as you do so. Place the thick slime that forms
into your hand and knead until it feels dry. (There will be an excess of water
remaining in the bowl.) It will be wet, stringy and messy at first, but the
more you play with it, the better it mixes and the less sticky and firmer
it becomes. Store your slime in a zip-lock in the fridge. That's it!
A slightly firmer variation
This makes a firmer, dryer slime that will even bounce if it is kneaded enough.
Mix 4 tsp. (20 ml) water with 5 tsp. (25 ml) Elmer's or other white glue in
a small bowl.
Add 1 tsp. (5 ml) talcum powder and stir until thoroughly mixed.
Add 1 or 2 tsp. (5 or 10 ml) saturated borax and water solution. Stir four
a few minutes.
Remove the glob from the bowl and stirrer. Knead it for a while and it will
become drier. You will probably need to wipe off some of the excess moisture
from your hands with a paper towel from time to time. Don't be tempted to
wipe the glob with a paper towel as it will only stick. You can add a little
talcum to the surface if you are having trouble getting it dry enough. Store
in a zip lock in the fridge.
Artisan methods: design your slime
The thing that makes this particular slime work is the bonding of polyvinylacetate
(PVAC) molecules by the Borax (sodium tetraborate). The molecules (polymers)
are long to begin with, and they are tangled, which is why the glue is so
viscous. Once the Borax links up some of the molecules, it becomes even more
viscous. Not all of the molecules hook up, though. The more that do, the more
viscous it becomes, until it reaches a point where it barely flows at all.
The amount of attachment that occurs among the PVAC molecules depends in part
on the concentration of Borax solution used. This is where we get the latitude
for making different consistencies of slime.
All of these variations use the same simple ingredients: a solution of Elmer's
glue, and a solution of Borax. The only variations are in the solution concentrations,
and in the ratios that the solutions are mixed together.
Most basic recipes suggest a 4% Borax (in distilled water) solution for an
average slime. This would be app. 1 teaspoon to half a cup (you've got it
easy if you use metric!)
The glue to water ratio is almost always 1:1, though I have encountered 1:.75.
This really won't effect the viscosity, however, the amount of water that
the slime retains does effect its "stickiness".
The typical glue to Borax solution ratio is 1:1. Ratios of 2:1 and 3:1 are
often cited. I have seen them as high as 7:1, but usually the Borax solution
was more concentrated. If you want to experiment with making different consistencies
of slime, I would suggest two things. First, measure everything metrically,
if possible. This makes it much simpler to keep track of concentrations and
ratios. Second, start with basic solutions of 50% glue and 4% Borax, mixing
them 1:1.
Experiment with increasing and decreasing the concentration of Borax solution,
all else being the same. The more concentrated the Borax, the more viscous
the outcome. You can actually produce something like a hard rubber ball if
the concentration is correct. The lower the concentration, and the closer
you approach a wet, sticky liquid. Keep notes so you can repeat the results
that you like. If you can't quite get the consistency you want, vary the amount
of water that goes into the mix.
Boric acid and borax method
This formula uses both boric acid and borax to produce a slime that seems
drier and stiffer. Mix a solution of 100ml water (preferably distilled), 10ml
rubbing alcohol, and 1 to 2ml boric acid powder. Mix well 20 - 30ml of this
solution with approximately 50ml of white glue. Make a borax solution of 1
- 2ml borax to 100ml water. Add the borax solution a teaspoon or so at a time
to the glue mixture. Stir continuously, adding borax solution until the desired
consistency is reached. As with the other white glue slimes, kneading will
make the slime drier and more viscous. If the slime feels too wet or sticky
after kneading, knead in a little more of the borax solution.
Gel type glues
Over the past few years several brands of gel type glues have been introduced.
Most of these make excellent slimes, and are able to be stretched into large,
clear membranes. These slimes can be made to be very elastic and have a nice
color and consistency. I have personally experimented with Elmer's School
Glue Gel, but there are several similar products available from other manufacturers.
Use the quick and easy method or the boric acid and borax method, above. If
they are a little sticky when they are stored, they will tend to be stickier
after a while. If this happens, see the following paragraph.
Slime overly sticky or runny?
If your white glue or gel glue based slime is too sticky or thin (runny),
first try kneading it for a while. Working it in your hands will help to mix
things up better, as well as remove some of the moisture. If it is still not
quite right, mix 1 part borax with 10 parts water. Dunk the slime into this
solution, remove and knead. The more you do this, the more "stout"
the slime becomes (to a point).
PVA Slime
This is often referred to as "institutional" or "commercial"
slime. This is the type that is generally found in toy stores. It is a little
trickier to make, not quite as safe, and more difficult to get the main ingredient
for (polyvinyl alcohol) than is the Elmer's slime. But it produces a superior
slime. Longer lasting, more transparent, and with a visual and tactile appeal
that is more, well, "slimy".
Assuming you can get hold of PVA, it is a fairly simple process to make slime.
First, mix a 4% solution of PVA and water. 4 % would be 40 grams of PVA to
960 ml of distilled water (of course you can adjust and make more or less).
Wear a mask and have plenty of ventilation when doing this! It helps to have
a heated magnetic laboratory stirrer (don't use one of your good kitchen saucepans
- it's best to use pyrex lab ware). Slowly, gradually, mix the PVA into the
distilled water. Heat it slowly, stirring the whole while, until the PVA goes
into solution. This will take 15 minutes or more. Do not let it boil. Once
cool, the solution can be stored in a stoppered bottle.
The 4% Borax solution is made by dissolving 4 grams of borax into 100 ml of
distilled water. It should go into solution without heating. This can also
be stored in a stoppered bottle.
Mix the two solutions in a glass or ceramic bowl. Do not use plastic. Start
with the PVA solution, and stir in the coloring, if used, and borax solution.
The standard ratio is 5 parts PVA solution to 1 part Borax solution. This
works well, but ratios have been quoted bother slime makers as 6:1, 20:3,
and as high as 200:15 (app. 13:1). The best bet is to start with the basic
4% solutions at 5:1, adjusting the ratio as necessary to get the consistency
you want. Store in a sealed container. No need to refrigerate. Keep it clean
and it should last indefinitely.
I read recently (and I apologize to the author, because I cannot find the
page again to reference it) that the consistency of PVA slime depends also
on the molecular weight of the PVA used.
Some archival art glues are actually a 5% PVA solution. It is almost certainly
more expensive to purchase the glue than it would be to purchase the PVA,
but, if you do happen to have a bottle around the house that you probably
wouldn't use otherwise, it should work (check the ingredients!) PVA is also
sold as a mold release agent for fiberglass molding, etc. Check with supply
houses for molding, boat repair, or auto painting. Also, some soluble bags
used in hospitals are made of PVA. If anyone knows how to make slime from
these, I would like to hear about it.
