Pulped paper for paper mache is basically made out of pulped paper mixed with a filler and a Binder.
It will keep in the fridge for very long period of time ..I have kept my pulped paper for 8 month once with not much ill effect , having to only add a little Paper Paste to make it workable again

PAPERS

I mostly use shredded office paper and I usually mix a large batch as it is plentiful . ( Great for building larger projects ).
You can also use tissue paper or toilet paper as a base .Those will make the final product finer ( nice for smaller projects and finer features ).
Of course you can also use Newspapers and even a little Sawdust mixed with it .
.Or try using egg cartons . Corrugated cardboard the final pulp will be a natural brown colour Experimenting is what its all about.

FILLERS

I mostly use a little bit not much plaster of Paris or Spackle for large projects .
For very large projects such as building houses successful experiments have been made with adding cement to the mix and forming brick much like Mud Bricks or rammed like Adobe .A product known as Papercrete.
I like to use clay for smaller project .This can give a very fine finish when mixed with toilet paper or tissue and can be burnished with a little water when dry .

BINDERS

Those are adhesives .I use both Pastes and Glues.The paste gives it a nice smooth feel and the glue adds strength.
Paste :
I use “ Polypaper ” paste exclusively for craft as it is not toxic.
Some recipe will tell you to use wallpaper paste but be aware that most wallpaper paste have a Fungicide added and this is toxic ..
Glue :
I use a good quality PVA glue ( white woodworking glue)

OTHER ADDITIVES :

You will also need a little bit of boiled linseed oil to add to your mix
Some bleach or as an added security against mould
Oil of cloves or Lemongrass oils as an insecticide if you wish

HOW I MAKE MY PAPER CLAY

Fill up a large pot with shredded paper ( I use a lot of office papers )
Cover with water and boil for 20 minutes to half an hour , this will break down the fibers some .At this point you can add some saw dust if you wish .
Let it cool down and add some cold water .I use a plastic rubbish bin to do that .You can now add 3 or four tablespoon of bleach to stop the pulp going sour .
Use a blender and run this through a blender until it’s a smooth pulp ( much like making hand made paper ) .
Empty the content of your blender in a strainer ..I use a large plastic flower pot lined with either nylon fly wire or shade cloth but any small holes strainer will do .Compress the pulp between your hand to further squeeze out the water

MIXING THE PAPER CLAY

Mixing the clay is mostly done by feel so quantities are variable

In a plastic tub put as much pulp paper as you can knead into a dough .

Separate the fibers by breaking up any lumps and rub a little plaster of Paris through it I don’t use a lot of plaster maybe about 3 tablespoons.
At this stage I also sometimes add powdered clay and sometimes Oxides to colour it
Note :- in papercrete they rely mostly on adding cement and water but that’s an other story .
Rub the clay and the plaster of Paris thorough the fibers using the palm of your hands.
Sprinkle a few Teaspoon of Boiled linseed oil and rub through it .You can now add the oil of cloves or lemon oil as an insecticide if you wish ( I feel that ,probably it was more important to do this in the days of using flour paste ) .but never the less I like to add some .

Next sprinkle some Polypaper paste through it and start kneading , if the mix feel a little dry add some water .As the paste swells up you will feel the dough getting slimy and smooth ( approx 15 minutes ) let the mixture settle a little for the grains to swell .Then add PVA glue , maybe about a cup , that all depends how strong you want the mixture to be and again the feel .
The feel should be smooth to the touch a little like clay and a little like a bread dough .

Well that’s about it ..You can now Apply it to an armature , mould it , smooth it , and or emboss it with various texture .Be sure to keep your hands and your tools slightly damp when working with the paper clay .

It can be sanded too when dry.