Wither art thou, Slimer?

July 6, 2009 9:25 PM

Science, why hast thou forsaken me? Help me work out why my PVA slime isn't slimy.

School holiday time. Thinking of neat science-y things to do with my seven-year old niece. Slime seemed to be the obvious choice. The recipes online all seem much the same - a 50/50 solution of white PVA glue and some borax solution, combine the two solutions, voila, slime.

The first batch was made according to these instructions. I combined both mixtures and waited. There was a turbulent cloudy effect, after which every drop of food colouring I added to the glue solution was ejected. I was left with a strange white putty they yields to gentle pressure but instantly shears or snaps if you try to stretch it.

Some more googling suggested that adding too much borax solution would cause 'cross linking' in the polymer and create hard putty. Using these instructions, I added the borax solution a teaspoon at a time to a half-cup of glue solution. Nothing. Nothing. Nothing. Then suddenly, the same fleeing of the food dye and the same goddamned putty in the bottom of the bowl.

Is it the glue? It's just white PVA wood glue. Help me, science geeks!

posted by obiwanwasabi to Science & Nature (5 answers total)

From all of my childhood experiences, this sounds like the proper results to the glue+starch experiments. I added color afterward with magic markers, but it definitely would shear with some tension. It would "drip" drippily, dry out after a while, turn rock hard and become one with the garage carpet (yeah, we had carpet in our garage). It stretches with gentle tension, but not too much. The shear is part of the neat-ness. Acts like a liquid and a solid AT THE SAME TIME!

Have you tried using liquid starch instead of borax? That's what I always used.
posted by that girl at 11:19 PM on July 6, 2009

Also, we always used Elmer's Glue. I don't know if that makes as much of a difference.
posted by that girl at 11:19 PM on July 6, 2009

I'm curious as to whether or not the glue was actually PVA and to what concentration? Then the next question is what else is mixed in with it? Would any of the other chemicals interfere? Ideally, a pure PVA glue is what you want (PVA + water).

When I did this in school, I used powdered PVA which is cheap to buy (if you're a school), but more expensive otherwise.
posted by plinth at 3:22 AM on July 7, 2009

Response by poster: The glue was Selleys Aquadhere Interior. It just says 'PVA glue'. According to its MSDS it's made from:

Polyvinyl acetate 30-60%
Water 30-60%
Vinyl acetate <1> 2-(2-butoxyethoxy) ethanol <1> Non hazardous component(s) to 100%

All the instructions I saw said to dilute it with the same volume of water (so half water, half glue). A heaped tsp of borax powder in 250ml of water. Added the borax all at once - fail. Added it a little at a time - fail.
posted by obiwanwasabi at 5:18 AM on July 7, 2009

Response by poster: Argh - stupid less-than sign interpreted as an HTML tag. Worked fine in preview. That's less than 1% vinyl acetate and less than 1% the ethanol stuff.
posted by obiwanwasabi at 5:20 AM on July 7, 2009