For some artists, paint is not enough. It is there as a base to be embellished; a medium that on its own is not the entire message.

String, paper, bits of cloth; many modern masters used the plasticity of oils as a starting point rather than as the end in itself.

The obvious examples are Picasso and Braque with their incorporation of tickets, bits of posters and newspaper cuttings that developed as Synthetic Cubism, while Francis Bacon sometimes added sand to his paint, and blew dust from the studio floor — of which there was plenty — on to his canvas.

Prominent East African artists prone to expressing themselves through mixed media include Beatrice Wanjiku, who made a series of paintings dealing with memories that included x-rays and photographic negatives.

Then as well as creating additional depth, both physically and of meaning by loading the picture plane, there are those who seek greater dynamism by rubbing, combing and gouging the surface, and in some cases by creating patterns when priming the board or canvas, which gives a rougher, more responsive base for their brushes.

(Sometimes it can be quite accidental. I remember a small plein air painting, oil on board, by Adolphe Valette, the minor French Impressionist best known for his studies of Manchester, my home city, in which an insect had become trapped in the paint and ended up as part of the impasto.)

It is a common technique to score the paint with the reverse end of the brush; called sgraffito, it reveals the colour beneath creating depth and adding vigour. The technique is used by many painters who locally include Patrick Kinuthia and his acolyte Coster Ojwang’.

The end is a truth known to the artist to be told to the viewer; the means secondary to that quest.

Or to put it another way, all’s fair in love and war.

One East African artist seemingly incapable of allowing paint to speak for itself is Samuel Njuguna, currently showing at the Banana Hill Art Gallery.

Many Banana Hill artists are enthusiastic decorators, sticking sparkly stones, sequins, bits of tape measures and even zip fasteners to their pictures.

Njuguna, however, in his scenes of everyday life, attempts to add vitality by applying a thick coat of primer to the canvas that he then combs in swirling patterns as a ground on which to create.

A full time artist since 2006, he trained at Banana Hill and, still not yet 30, he told me he had tried painting on a flat, primed surface but that the finished work lacked excitement.

Of his 34 paintings almost half include cyclists, either as the central subject or appearing incidentally. Cyclists he sees as speaking for much of the African lifestyle and are therefore symbols to which most viewers can relate.

Njuguna draws well, rooting some reality to his otherwise otherworldly scenes with their vaporous air and sometimes startlingly bright palette.

Another favourite technique of his is scumbling; that is dragging a wash of paint over an existing passage, allowing the new layer to break up, revealing the underlying colour. When he pulls it off properly, this gives a shining, almost luminescent surface, but, added to his relentless under-combing, it also creates texture upon texture and a flourishing of technique that overwhelms the substance.

The ridges created by his combing have nothing at all to do with the direction and rhythm of the subject painted on them; they appear as purely decorative and add nothing of value. It is a classic case of too much of a good thing — effect piled on effect until the point gets lost and we are left with flash, dash and nothing to see.

It is unfortunate that the most striking thing about Njuguna’s exhibition is not so much the scope of his subject — ordinary life made memorable — and the drawing that underpins it, nor even the paint that dances and sometimes shimmers to the eye, but rather the artist’s insistence on painting on top of an irrelevant pattern.

Nonetheless, these are pleasant paintings, well observed and he has at least made this quirky style his own... but they do rely too heavily on their decorative effects; which is a pity because that detracts from the potential power of the work and its obvious strengths.

The adage “less is more” fits well.