Binding Cereals

For this collaboration in the fall issue, we want to propose an activity to provide us with materials for the handicrafts made at school. That is why we recover a recipe to make glue with flour that has been known and used for a long time and is very simple to elaborate. Producing the glue used in school work and handicrafts is yet another way of reducing costs and making accessories and necessary tools for the school activities in an entertaining way. In addition, it is a pretext to enter the world of cereals, a group of plants that get their name from the goddess Ceres and represent the most efficient plant group; they are a sustainable and austere form of life. 

Cereals are plants that have almost no leaves, nor a woody texture, live around the world and can colonise the most inhospitable places, such as landscapes burned by a fire or extensive dry lands. The most well-known are those used for basic nutrition, such as rice, wheat, maize, oats, rye, sorghum, millet, spelt or barley. They are very valued for their nutritional qualities, since the seed, although very small, provides the essential nutrients for a basic diet.

Cereals provide the vegetal sugar par excellence, starch, which animals lack. Starch is made up of two types of molecules, amylose – which are units of glucose that form linear chains – and amylopectin – the chains of glucose units from which they stem. The characteristic of these two molecules, one long and one smaller, is that they form a compound when connecting with a water molecule. This is the basis of our product, glue. Glue is an adhesive material used for putting up posters or painted wallpaper and to do craftwork with paper and cardboard or papier-mâché. It is the perfect solution when you have to glue a lot of things and you do not want to spend money on synthetic glues. Although many know that glue is basically white flour of any cereal, the exact way of making it is an art that few people today master.

ACTIVITY: HOME-MADE GLUE WITH FLOUR

Glue with flour, also known as paste, has been used for a long time, and it is also very easy to make. We are going to show you the recipe and give you some advice on how to preserve this glue for a longer time. The best option is to make it the day before and prepare only as much as necessary for the activity, since it will last three days at most. It is a light adhesive, so children can use it.

Method

— Prepare a cup (¼ litres) of water and heat it.
— Meanwhile, mix three tablespoons (45 ml) white flour and three tablespoons cold water and stir to avoid lumps. We can use rice or maize flour instead of wheat flour to avoid lumps altogether.
— Then, add this paste to the hot water, over a very low heat, and stir until the substance can be described as thick. If we let it fall from a spoon, it must not drip.
— Let it cool down.
— If the paste sticks to the pot, leave it to soak. If you use rice or maize flour, it thickens quickly and the paste will not stick so much to the bottom of the pot.
— If necessary, a Japanese strainer can be very useful to dissolve the lumps that may form. You can also dissolve them with your fingers.
— Keep the paste in a clean container.
— If you only use part of it, keep the rest in a jar. In order to better preserve it, you can boil it or leave it in the refrigerator.  

Some tips

— You can bain-marie a pot to prevent the mixture from sticking to the bottom.
— You can exchange the flour for cornflour or for maize or rice flour if you so desire.
— The paste usually lasts a week at most; that is why it is advisable to make only the quantity that is needed.
— Possibly you will need a wooden spoon or something similar to stir the glue, because it thickens quite a bit as the water evaporates.
— The optimal consistency can change depending on your needs, but it usually has the consistency of normal paper glue.
— If you add a teaspoon of tea or vinegar, the pastes will last longer (but still not much more than a week). It is ideal for glueing cardboard and paper. You can also add a few drops of lime juice.
— If you add a little copper sulphate, it will last a lot longer without decomposing. If you want to use the glue for papier-mâché, that will prevent insects from spoiling it.
— If the glue has black or green spots, it has started to decompose and must be discarded.
— Always use clean utensils. Not doing so can accelerate the decomposition of the glue.

Mª José Carrau, Olga Ibáñez i Pepa Rey. Teaching Team of the Botanical Garden of the University of Valencia.
© Mètode 75, 2012.