I pride myself on nearly always using traditional materials and methods - The Craftsman's Handbook  (Il libro dell'arte). - Cennino d'Andrea Cennini  is the definitive renaissance guide to preparing canvas etc for painting. Lets face these paintings have been knocking about for the best part of 600 years so they must have got something right! However  I do use some homegrown modern equivalents at times!
Perfectly robust and deep stretchers can be made out of well seasoned 2 by 1 (I think the metric equivalent is 25 x 50 mm). Be sure to run a strip of quarter inch quadrant along one edge with glue and pins - this will hold the canvas away from the flat edge of the wood. Depending on how much of a perfectionist you are the quadrant can be rounded off with sandpaper and the pins sunk into the wood. Mitre the ends at the length you require and assemble the stretchers with frame clamps glue and metal L shaped brackets for strength.
I use linen these days although for a long time I used 12 oz Cotton Duck (10 oz is OK but has an obvious weave, 15 oz is like handling the sails of a Nelsonian Man-o-War!)
I now get my Linen and stretchers form Russell & Chapple in Covent garden in London. They have been supplying canvas for stage sets for donkey's years and have the biggest range of cloth for art and stage I know. ( they are also suppliers of the Spectrum range of Oil paints)
Having assembled the stretcher (remember to order cross bars for lengths over 36”: canvas contracts viciously when sized and primed and will pull surprisingly thick lengths of wood into a bow!) lay it out over the canvas so there is a minimum of wastage. Allow 2-3 inches extra to of the width of the stretcher bars and cut with a sharp knife (you should be able to run the blade through the weave fluidly)
You can use a stable gun although I have always preferred blue steel tacks (1/2”) hammered neatly into the back of the stretcher. Pin halfway along one edge but at first only knock the tack in halfway. Repeat on the opposite edge, pulling the canvas taught but without pulling it too tight. Canvas stretching pliers can be used but I find they invariably pull the canvas too tight causing warping when the size is applied. Work systematically around the canvas until about 5 inches from the corners. Treat the corners like the “hospital corners” you find on well made beds pulling the cloth into a neat triangle over the end of the shortest edge and pin it down to the back. (did I mention I was quite pedantic about this?)


Art Materials: suppliers of paint, brushes, canvas, stretchers and printmaking materials for artists
Many artists these days prime the stretched canvas with an Acrylic Gesso Primer which will support both Acrylic or Oil paint. I find these this on its own tends to go baggy when applying paint too vigorously and lacks the satisfying spring and resistance of the traditional Rabbit Skin Glue. This come in a crystalline powder form in lb or 1 Kg bags and will keep for years if kept dry. I bought loads from Cornellissens years ago and it has never left me down. Cornellisens are the place to go for top quality paints, inks and the pigments and oils to mix your own! The shop in London is like an old apothecary's shop and entering it is like entering a different age.
Spoon three tablespoons of size into an old baked bean can and top up with hot water. Place the can in a saucepan half full of hot water and bring slowly to the boil. Have a stick ready to keep stirring and simmer until all the size has dissolved. This stuff smells absolutely disgusting and is very sticky, but will easily wash off hand and clothes. Leave the size to cool down and it will start to solidify into a cloudy sand coloured jelly or stock. This can kept in the fridge and reheated as often as required but will go mouldy very quickly if not reheated occasionally..
To use heat the size to dissolve it and allow to cool until it is still warm and liquid but has started to thicken. Lay the canvas face up on the floor and spread size over the surface using a kitchen sponge. The size should be liquid to penetrate the weave and soak into the canvas without dripping though. Sizing the canvas upright increases the chance of the stretcher warping and can cause the size to run down the flat surface. Despite your best efforts the Canvas will often warp several inches out of true - DON'T PANIC!! Canvas and linen in particular contracts when wet but in most cases will be pulled flat by the stretchers when dry. Allow at least 12 hours to dry completely. The stretcher should be almost as feel like a drum. The size will have darkened the canvas and should reflect like little pinprick stars an the back of the canvas.
Brushes, Paints, oil and acrylic
I use both acrylic and oil paints. It is perfectly OK to paint using acrylics and then paint over with oil, just not the other way round! The original and arguably the best acrylic is Liquitex but Golden gives them a gun run for their money. I use Spectrum studio oil paints and pro arte brushes. Don't spend a fortune on expensive brushes - they wear down surprisingly quickly and you will often find the cheapest will become your favourite.
There are many types of easels: Desktop easels, which can store brushes and pencils and which sit on a table, portable easels that collapse to nothing and resemble something out of “war of the worlds” when finally unfolded, and studio easels which can handle vast canvasses. The Windsor and Newton Radial easel has been my personal choice for the last 30 years. It is as far as I am concerned the artist’s weapon of choice; The AK47 of the art world!
Not without reason is this the easel you will find in every serious art school and evening class. Its cheap; (hovering between £40-£70 since the 1980's), robust and versatile. It will handle anything from a tiny watercolour to a 6 foot square canvas and can be folded up and stacked in a corner when not needed. adjusting the various butterfly nuts that hold it together can be a bit of a chore, but this beast will outlive you!
Ryepress resources is an Amazon “Astore” in which I have gathered together a selection some of the Art Materials and equipment that I have used personally and can therefore recommend.