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Forensic Science International, 46 (1990) 33-35 Elsevier Scientific Publishers Ireland Ltd. 33 AUTHENTICITY JUDGEMENT WITH THE HELP OF PAINT-BRUSH TRACES LUCIAN IONESCU Criminaltitic Examinations Central Laboratory, Ministry of Justice, Bucharest (Romaniol Summary The methods of authenticity determination on the basis of paint brush traces were described. Key words: Authenticity determination; Paint brush traces; Picture examination The association of the term authenticity with trace examination can be explained by our attempt to deal with two problems, connected to a certain point: that of identifying the paint brush as the object which has left the traces and that of identifying the person who has handled the brush. In both cases we are concerned with verifying a hypothesis and proving the truth. Paint brush traces belong, as far as we know, to a field which has less been studied and even less turned to practical account in forensic sciences; perhaps this is due to their variable nature. The approximately parallel lines drawn by the hairs of the brush in the wet paint cannot give a constant image, identical for two successive brush strokes, as is possible with traces left by objects hav- ing a stable external structure (fingers, tools, shoes, tyres, etc). On the other hand, the configuration of the brush traces is influenced, more or less, by sev- eral factors which cannot be ignored. These are: 1. The type of brush: according to its function (painting, dyeing, varnishing). 2. The form of the brush: (a) rounded, with either an even or a curved end; (b) flat, with either a linear or a rectangular end; and (4 spindle-shaped, tapering towards the end. 3, The size of the brush: ie the extent of the contact. 4. The hardness of the brush: soft or stiff, according to the density and the origin of the hair (hog, marten, silk, plastic); included here is the possibil- ity of artificial hardening due to unwashed paint. 5. The consistency of the substance (usually paint): the type as well as the amount of pigments, binders and dilutents. The temperature of the sur- rounding also exerts its influence. 6. The support: An even surface allows light, continuous brush strokes whereas a rugged one produces ridges and interruptions when “jumping over obstacles”. The paints have some other elements to be taken into 0379-0738/90/$03.50 0 1990 Elsevier Scientific Publishers Ireland Ltd. Printed and Published in Ireland

Authenticity judgement with the help of paint-brush traces

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Forensic Science International, 46 (1990) 33-35 Elsevier Scientific Publishers Ireland Ltd.

33

AUTHENTICITY JUDGEMENT WITH THE HELP OF PAINT-BRUSH TRACES

LUCIAN IONESCU

Criminaltitic Examinations Central Laboratory, Ministry of Justice, Bucharest (Romaniol

Summary

The methods of authenticity determination on the basis of paint brush traces were described.

Key words: Authenticity determination; Paint brush traces; Picture examination

The association of the term authenticity with trace examination can be explained by our attempt to deal with two problems, connected to a certain point: that of identifying the paint brush as the object which has left the traces and that of identifying the person who has handled the brush. In both cases we are concerned with verifying a hypothesis and proving the truth.

Paint brush traces belong, as far as we know, to a field which has less been studied and even less turned to practical account in forensic sciences; perhaps this is due to their variable nature. The approximately parallel lines drawn by the hairs of the brush in the wet paint cannot give a constant image, identical for two successive brush strokes, as is possible with traces left by objects hav- ing a stable external structure (fingers, tools, shoes, tyres, etc). On the other hand, the configuration of the brush traces is influenced, more or less, by sev- eral factors which cannot be ignored. These are:

1. The type of brush: according to its function (painting, dyeing, varnishing). 2. The form of the brush: (a) rounded, with either an even or a curved end; (b)

flat, with either a linear or a rectangular end; and (4 spindle-shaped, tapering towards the end.

3, The size of the brush: ie the extent of the contact. 4. The hardness of the brush: soft or stiff, according to the density and the

origin of the hair (hog, marten, silk, plastic); included here is the possibil- ity of artificial hardening due to unwashed paint.

5. The consistency of the substance (usually paint): the type as well as the amount of pigments, binders and dilutents. The temperature of the sur- rounding also exerts its influence.

6. The support: An even surface allows light, continuous brush strokes whereas a rugged one produces ridges and interruptions when “jumping over obstacles”. The paints have some other elements to be taken into

0379-0738/90/$03.50 0 1990 Elsevier Scientific Publishers Ireland Ltd. Printed and Published in Ireland

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account, too: the elasticity of the canvas, the nature or thickness of the ground, the condition of the canvas (new or overpainted).

7. The position of the brush: How it is grasped (by the end of the handle, at the bottom, in the middle).

8. The motion of the ham-k The arm stretched or bent, leaning on the elbow or on the joint. The direction of the movement and the angle of applying the brush are conditioned by the position of both the person and the sup- port: vertically, horizontally, at ‘eye’ level, higher, lower, etc.

At the first sight, the dynamic nature of brush traces and the fact that they are conditioned by various factors are not likely to offer too many footings in identi- fication examinations. But a careful consideration proves quite the opposite.

First, those factors conditioning the traces are limited. For instance a trace cannot go beyond the limits of the extension radius of the hairs. Second, not all factors mentioned above are aleatory. Those related to the characteristic features of the brush allow, when combined, a relative particularization of brush strokes, a premise for a generic identification.

In certain circumstances the brush may provide a particular identification of a special kind, for instance when combining broken component parts to remake a whole. A layer of paint which has come off in an accident or has been found on a burglar’s tool or on a criminal’s coat may sometimes be reintegrated into the mass it belonged to. When the brush traces on two fragments match - the lines of one continuing in the other - we may conclude that both belonged to the same brush stroke. They were painted with the same brush: the method can be used not only in the situation in which we have broken pieces whose edges meet and match but also in the case of pieces coming from different parts of a support.

Except for the above mentioned case, in which we have two or more objects painted simultaneously, it is impossible to identify a brush. It is undeniable that deterioration of hairs individualizes a brush, but this deterioration is not reflected accurately enough in the morphology of the stroke and cannot prove its uniqueness.

Differences, on the contrary, are convincing. When the incriminated trace is completely different from the trace drawn with the presumed brush, it means we do not have the right brush.

If traces play a limited part in identifying the paint brush, they play a capital part in authenticity judgements.

The brushstroke is a vivid gesture, including both dynamism and energy. As an image of the artist’s unconscious impulses, the brush stroke has been com- pared with the strokes of writing and can be called “pictorial writing”. It includes not only constitutional factors, but also conceptual ones, rational and volitional such as the rendering of forms, the amount of paste, the amplitude of the brush stroke, the accents, etc. All this forms a true pictorial modus oper- andi, an individual stamp characteristic for each artist and which is recognizable within comparative examinations. This cannot be imitated even if well known by forgers.

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So, if we can find out great differences between the paint layer structure of our painting and that of other paintings belonging to the artist supposed to be the author we can speak of forgery. The differences are relevant only if the original paintings compared to belong to the same period, as the manner of painting changes along one’s career as an artist.

The roughness of the brush strokes can be seen when illuminating a canvas with either a parallel pencil of rays or with one forming a sharp angle with the surface. When examining the drawing and the strokes the most adequate light to illustrate the depth of layers is the monochromatic sodium light which blurs the colours.