Take 200cc of "water glass", add 800cc of distilled water and stir. To this add 400g of sodium hydroxide (caustic soda).
Important safety precautions: The sodium hydroxide solid must NEVER be handled, use disposable gloves. When the sodium hydroxide dissolves in water it produces a great deal of heat so it must be added a little at a time and each  portion allowed to dissolve before more is added. If the solution becomes very hot leave it to cool before adding more sodium hydroxide.
The solution is VERY caustic and it is particularly damaging to the eyes, use eye protection when making and handling it.
It also ruins clothing. Water glass is also known as "sodium silicate solution" and "egg preserver", It used in fire proofing fabrics, for waterproofing walls and making "chemical gardens". Caustic soda is used for clearing drains and available from any chemist. The solution cannot be made by dissolving solid sodium silicate.
This solution will be the same strength as the concentrate, and so will need diluting - about 1 part concentrate to 4 to 8 parts water, depending on the photoresist used and temperature. Edit: I can confirm that sodium metasillicate pentahydarate crystals work. I've tried ordering universal developer crystals and sodium metasilicate pentahydrate crystals, both work for developing positive photoresist. The metasillicate pentahydrate I've used was labeled 57%. In both cases I've used a teaspoon of the powder per 200ml of warm tap water. The solution doesn't last as a developer so developing should be done right after dissolving the crystals. My exposure time was about 3.5 minutes, but this will vary depending on the exposure box. | 