HARD WICKE 'S SCIENCE-G OS SIP. 



169 



ANOTHER WAY OF MAKING PLASTER CASTS 



OF FISHES, &.C 



By J. H. LAMPREY, Editor of "Industrial Art." 



AVING made many hun- 

 dreds of casts of sea and 

 fresh-water fishes, and 

 having tested every method 

 I have seen employed, I 

 have come to the con- 

 clusion that the simplest 

 and most effectual plan 

 is the following : — Place 

 the fish on a board, pin 

 out its fins and tail neatly 

 with ordinary pins, pass some brown paper or 

 tow inside the mouth, in order to raise the 

 eye if sunken from any cause, or to force asunder 

 the lines of the mouth and operculum, which 

 become contracted after death ; place some putty 

 under the dorsal fin, and then trim away all that 

 extends beyond its outline. The fish is now ready to 

 mould from. Next, take a long strip of thin sheet zinc, 

 about two or three inches deep, and place it in the 

 form of a wall all round the fish, and about one inch 

 from it, at every point ; partly split asunder a fire- 

 wood stick, and with it clip the free ends of the zinc 

 wall, drive in a twelvepenny nail at each end to keep 

 this wall steady. Bear in mind that both the pin 

 points and the nails need only sticking in the wood 

 in the most temporary way. Now take some plaster 

 of Paris in a cup, and, after mixing it as thin as cream, 

 smear the inside of the zinc along its edge where it 

 comes in contact with the board, and pour some down 

 the place of junction near the clip. In a few minutes 

 this extemporized dish is water-tight ; now nearly fill 

 it with the cleanest water procurable, and sprinkle 

 rapidly from a ladle some common or second-rate 

 plaster of Paris, coloured with a little washing-blue, 

 over the fish until it is just covered with plaster ; now 

 lay four pieces of strong cord across the fish, leaving 

 the .ends over the sides of the zinc receptacle ; having 

 arranged these cords so that they just touch the 

 plaster, without any loss of time continue to pour in 

 the dry plaster until the vessel is full, or there is at 

 No. 164. 



least one inch of plaster over the highest part of the 

 fish, then remove the cords by lifting each end at 

 once ; as soon as the plaster is set, break away the 

 zinc band, and strike the board sharply with a hammer 

 until the plaster becomes detached ; if it sticks 

 closely, pour a pail of water over the plaster, and it 

 will at once give way. Turning over the mould we 

 have the fish buried in the case, or mould of plaster, 

 with only a very small portion of the underside of the 

 fish exposed where it rested on the board. Proceed 

 to break away the thin coat of plaster which has 

 settled along the margin until only an inch of plaster, 

 or even less, remains from the fish outline ; remove 

 the putty from the under portion of the back fin, pull 

 out the padding from the mouth, and then lift up the 

 tail, draw the thin end of the fish slightly backwards 

 and upwards; be careful not to injure the surface, but 

 get out the jaws and raise out the back. Use no force 

 that would break the fine surface of the mould. If 

 need be, open the fish, and remove the intestines, 

 and so give more space for getting out the fish ; this 

 being successfully accomplished, dip the whole mould 

 in water, and then pour in a spoonful of naphtha, 

 which will cover the cast with its oily adhesion ; wash 

 it again with water, and place the mould in a vessel 

 of water ; pour in the plaster so that it will fill the 

 interior of the mould, but have ready some copper 

 bell-wire bent to fit the tail, back fin, and pectoral 

 fin, if raised at all. No care need be bestowed upon 

 the shapes of these wire supports so long as they are 

 flat and just roughly define the form of the tail and 

 back fin ; the plaster must be poured over the mould 

 in sufficient quantity to represent the board on which 

 the fish was resting. By casting under water there 

 are no air-bubbles, and the plaster is homogeneous. 

 After a few hours, which may be profitably spent in 

 cleaning up the work-table of all the filthy plaster, 

 the plaster-mould must be plunged into cold water, 

 and the table on which it i - ests must be struck with a 

 mallet. To cause the mould to separate from the cast, 

 take a chisel, and where the line is defined by the 



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