Slime

This is an excerpt from a really great web site. http://bizarrelabs.com/slime.htm.
What we 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.

Green jelly ooze
This makes a nice jelly like ooze. First, you need to make some iron acetate. Do this by placing some steel wool in a jar, and adding enough white vinegar to cover it. Let this stand for five days to a week. Pour off some of the mixture into another. In yet another glass receptacle, add equal parts (a tablespoon or so) of this mixture and household ammonia. Use plain ammonia, not sudsy, and not scented. Instant weird green jelly ooze. Note: I haven't gotten this one to work correctly. If you know this slime, and I am leaving something out, please let me know.

Silly Putty™
You can't really make this at home (unless you have the resources of Dow Corning) but a lot of folks are curious as to what Silly Putty™ is made of.
Ingredients for Silly Putty™ (Dow Corning 3179 Dilatant Compound)
Percentages by weight.
65% Dimethyl Siloxane, hydroxy-terminated polymers with boric acid
17% Silica, quartz crystalline
9% Thixotrol ST
4% Polydimethylsiloxane
1% Decamethyl cyclopentasiloxane
1% Glycerine
1% Titanium Dioxide

Play dough
Not technically a slime, but it somehow seems to belong here all the same.
Non-hardening variety
Mix well
· 1 cup (250 ml) flour
· 1/2 cup (125 ml) salt
· 2 tsp. (10 ml) cream of tartar
· 1 cup (250 ml) water
· Few drops of food coloring
In a pan heat 2-tbsp. (10 ml) vegetable oil. Add the other ingredients, and cook 3 minutes. Stir constantly. Let the dough cool. Store in plastic wrap in the refrigerator.

Hardening variety
Mix well
· 1 cup (250 ml) flour
· 1/3 cup (83 ml) salt
· 6-8 tbsp. (30-40 ml) water
· Food coloring, if desired
Add the water gradually, using only enough to produce a workable consistency. To set, bake at 300° F until hard.

More recipes!
Here are a few other recipes that have been sent to me. I haven't tried them yet, so no guarantees!
"Just a quick FYI for your interest: many years ago I found out that one can make a substance somewhat like Silly Putty by simply mixing sodium silicate (which used to be available in drugstores (no longer, alas!) and which was also used to coat eggs - it sometimes was carried as 'egg preserver'!) with everyday rubbing alcohol. The two combine to form a jell-like substance that exhibits flow somewhat like putty. The ratios are not terribly critical."

- Submitted by Bert Koehler
"One of my students went home and tried to duplicate the slime, but didn't have borax so he used Chlorox (liquid laundry bleach) instead. The result, which he brought in, was not slimy and much more like "Silly Putty". You might want to give it a try."

- Submitted by Cassandra L Whitsett
Slime rules and safety
· Slimes can wreak havoc with plumbing, so don't throw them down the drain.
· Always wear a mask when mixing PVA.
· Use distilled water for all solutions for best results.
· Keep slimes away from anything they could damage. They can dry into fabric, and any dyes they may have can stain. All slimes can potentially harm surfaces, especially wood.
· Supervise small children when playing with slimes so they do not ingest any.
· Some people are allergic to Borax powder. Wearing rubber gloves when mixing should help.
· Slimes using Borax solutions work best if you pour the Borax solution into the other solution, rather than the other way around. Coloring should be added before the Borax.
· Use metric measurements whenever possible. This will make it simpler to experiment with different concentrations and ratios.
¹Thanks to Professor Bruce Knaur of SUNY at Oneonta for these definitions!