by Arthur Chater
Many thanks to A.C. for permission to reproduce this
Materials
A slightly heavy-duty press made of 1 inch weldmesh © GT
The method of drying plants developed by Professor J. Madalski of Wroclaw in Poland has been used by the great majority of Polish plant collectors for the last 50 years. The method was demonstrated to me in 1962 by Professor Madalski and I have used it successfully since then in a wide variety of conditions and climates. For British readers, the best introduction to the method is a paper by Madalski entitled ‘A new Method of Plants’ Drying for Herbarium’ in Fragmenta florstica et Geobotanica (Krakow) 3(2): 69-76 (1958). For my interest in and knowledge of the methods I am entirely indebted to Madalski. The following account describes a modification of his method, making use of materials readily available in Britain and introducing a few new elements.
Theory
Conventional drying techniques generally involve pressing the plant between sheets of absorbent paper in a thick press. The moisture from the plant is absorbed by the paper, which is replaced at intervals by dry paper until the plant is sufficiently desiccated. In Madalski’s method the plant in pressed between porous sheets (either paper or sacking) in a thin press. The moisture from the plant evaporates through the sheets, and there is no need to change the sheets. Because of the easy circulation of air and evaporation, heat can be applied without any danger of the plants blackening.
The presses described below are designed to dry plants that will be mounted on Kew-size (10 1/2, x 16 1/2 inches) sheets. For no logical reason it has been the practice to use presses, the paper of which is substantially larger than that on which the plants are to be mounted. However, since a small press dries more quickly than a large one, and a space must be left on the mounting-sheet for a label, a press is more efficient if it is slightly smaller than the mounting paper. It is also lighter and easier to transport.
Press
The framework of the presses is made of welded steel mesh (BRS Weldmesh – galvanised, with a 1/2-inch square mesh, in rolls 1.2m or 47 inches wide). This is cut into rectangles 9 1/2 x 15 1/2 inches (24.3 x 39.3 cm), the sides of which contain 19 and 31 squares. The long axis of such a rectangle fits exactly 3 times into the width of a roll. The mesh is cut off flush with the wire along the edge and filed smooth. The mesh has a natural curvature when supplied and the rectangles are cut out so that the long wires are on the convex side. The convexity, is then somewhat flattened out by hand so that when the press is tied up an even pressure is obtained over the whole surface. (The convexity should not be more than 1/2 inch at the middle of the rectangle).
Binding of edges
For comfortable handling the edges can be bound with self-adhesive tape. 260 cm of tape 2.5 cm wide is needed for each press (Bondfast tape 5 cm wide, needing to be cut down the middle, is available at hardware shops). The strip is folded over the edges of the mesh and pressed together and stapled between the wires.
Cord
Nylon or preferably terylene cord 1/12 in. (2 mm) diameter (available from hardware or camping shops) is used for tying up the presses. 3 metres are needed for one press. and the cut ends are sealed in a flame.
Porous sheets
Ten or a dozen sheets of porous paper or sacking are needed for each press. They are 9 3/5 x 15 3/5 inches (24 x 39 cm), fractionally smaller than the framework of the press. Normal drying paper is as effective as anything, and should he thick with a rough surface. (Sheets or folded zigzags of sacking are as good. and I have found that scrim, sold at drapers and used for window cleaning, is the best sort. However, it is troublesome to seal the edges, and experiments show that little is gained over drying-paper either in lightness or in speed of drying).
Flimsies
Newspaper is effective and convenient: the sheets when folded should be exactly the same size as the drying paper. When travelling. it is useful to have a rectangle of very thin aluminium sheeting with sharp edges, of the same size. which can be used as a mask for quickly tearing newspapers to size.
The assembled press © GT
Method
The plants are best collected straight into flimsies in a collecting press (of the same size as the drying press or slightly larger) and need never be removed from these flimsies until they are to be mounted. The specimens must be carefully arranged in the flimsies before they are put in the drying press, since they will be dried before they are looked at again.
About five to ten flimsies, separated from each other (and from the mesh) by, only single sheets of drying paper, are placed in each press. Fewer should be used if the plants are succulent, and more if they are already very dry. The frames are placed on the top and bottom of the pile so that their concave sides face outward. They are then tied up as tightly as possible with the terylene cord, so that the pressure is evenly spread out and maintained. No further tightening is needed during drying. See also addendum note below.
In a suitable climate the presses are laid out in the sun. preferably supported at one end so that they are positioned to catch the ray’s of the sun at right angles (a simple bent wire support is convenient). If possible the presses are turned over at half-time. They can. in the Mediterranean sun, become too hot to hold and the contents dry in 3-9 hours. Allowing for an average proportion of more succulent plants, one can rely on drying thoroughly 80% of a day’s collection in one day in such climates. In cooler climates the outermost sheets of drying paper can be painted black and this greatly increases the speed of drying in the sun. If drying chambers are available, the presses are stacked upright in them and drying is extremely rapid.
For small-scale collecting while travelling the method is also ideal, since the presses are light and compact and can be dried overnight or in a few hours on radiators, in airing cupboards, in front of fires. or propped up inside a sunny window. An especially efficient method is to tie the press on to the outside of a car. Madalski claims that plants can be dried in such presses by hanging them up in the steam of a cooking-stove. The only obvious drawback is that with such speedy drying there is a greater danger of the specimens being over-dried than there is in conventional methods. Accidental soaking of the presses when they are laid out to dry seems to do no harm and they dry out again very rapidly.
Advantages
A great deal of labour is saved since there is no need to change drying papers. For collecting a given number of specimens in a given period of time, the equipment needed weighs about half as much as conventional equipment. It is extremely adaptable and can be used out of doors, indoors, in conjunction with drying-chambers, or can also be used for pressing plants in the conventional manner if this is required. The presses are rustproof and virtually indestructible. One press, complete with eleven sheets of drying paper, weighs 1 lb. 11 ozs.
Addendum note
The presses I made for use in the field were rather cumbersome to tie, and often to retie – after another interesting plant had turned up – so, experimenting with large bulldog-clips, I found that up to an overall thickness of about 25mm (1 inch) they were efficient and much quicker than cord, which I always contrived to tangle in a knot anyway. If you want to try them it is best to use clips with wire fold-back grips as other sorts are a nuisance. For a standard press you can get away with six large ones 50mm (2 inches) wide, a heavy-duty press may need only four.
G.T.
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