Having completed the Dragon Skin 3D painting of the dolphin once it was dry i varnished it with a clear varnish. I did this even though this IS just a copy piece NOT the final dolphin form simply because Dragon Skin unless sealed WILL absorb water & then crack to different degree's (depending on how soaked it gets after initially applied & dried). So as you can see the varnish was required.
The next step was to create a board around the dolphin form to contain the plaster when added. This would normally be done using modelling clay or plasticine, but i explained this prior. Using stiff card stock i chose a larger piece of card than the dolphin form & cut out a crude dolphin shaped hole in the card.
I then placed the dolphin form in the hole & secured the backside with tape as a temporary measure to hold the form in place until the first stage of the plaster casting was set in place. Now if you are making a 2 part casting or mold such as this is you need the first half or side of the subject being copied to be proud of the clay (card stock). As this is the first half or side to be burried in the plaster. It need not be 'exact' but the better you can do it the easier the final pieces will come together & be worked with.
Once i had that done it was time to make the 'box' to contain the plaster for the first stage of pouring. Since this is a small project & the card stock i am using IS quite strong a card box will work easily here. Make your box's at least 1 or 2 inches wider than the object being copied. Also make the 'depth' similar.
If this were a perfectly smooth surface on the box & the subject being copied such as glass or polished metal or even plastic then chances are i would not require a 'releasing agent', but it's not & i do. Now there are many, many commercial available & there are just as many 'home made' methods too. I personally find a layer of wax works with alomost every surface you could want to cast or mold. Of course seriously absorbant materials would bring they're own difficulties but then these would not be typically casting or molding materials anyway. Here i am using a simple floor wax. It's a durable wax but is extremely soft for application which suits my needs perfectly.
When applying the wax i find a soft bristle brush works best. Since i wanted to 'apply' more wax than i removed. Again if i were using clay or plasticine as the base concerns over the wax being absorbed & reducing it's releasing qualities would not be. Since i am using card stock i chose to give the card sections a good coating of wax to compensate. The dolphine form however having been coated in varnish only required a thin coating. To reduce streaks forming in the copied object try to brush gently & in the 'same' direction. I will be making MY copies of this dolphin form in paper strips so any 'streaks' that may form are not an issue to me. If the object is to be copied in a fine plaster then brushing in the same direction should reduce any streaks that form to be less noticeable & easier to gently sand out later.
Once again had i been using clay etc this stage would be self supporting. So i need a way of holding the whole thing level & steady whilst it dries. To do this i simply placed a few inches of sand into a box so that my project would sit in comfortably.
Now comes the plaster pouring. Unless you have experience doing this on a daily or very regular basis your going to need a way of measuring just how much plaster to make up to use. Plaster especially sculpting plaster can be expensive. Unless you know your project is going to sell & sell well you really don't want to be producing too much waste now do you. A simply way to guage just how much plaster to make up is to take something like rice or flour (any kind) then fill your box around your object to be cast exactly to the level your going to have the plaster at. Then pour the rice etc into a measure (a jug etc). Take note of the amount of rice that filled the casting box around your object - That's the amount of plaster your going to require mixed up. Simple huh? Now mix up your plaster as per the instructions that came with it. Then pour it into your box frame around your object. DON'T let the plaster gloop out suddenly or pour in a ripple manor. Pour the plaster in a slow & smooth fashion so it spreads slowly & evenly not folding over itself.
Your NOT making a cake so resist the urge to smooth out the plaster with a spatular or knife. Also ONLY POUR the plaster into one corner or side of the box too. The LESS scooping & shifting around YOU do directly by hand the LESS air bubbles your likely to trap. Air bubbles in plaster spell 'disaster'. They weaken the plaster structure & can appear right on a detailed section of the object your copying ruining the piece or at the very least giving you needless repair work later. Once you have all your mixed plaster pourd in take a firm hold of the sides & for a few seconds 'firmly tap' the whole thing down on a solid surface. This will force the bubbles you may have produced to rise up through the plaster & break surface. Even the experts get bubble formation somethimes & it only takes one to cause problems. How do you know when you got them all? Well you don't but you can be sure you got MOST if not all. How do you know when enough tapping has been carried out? One of two things will happen or they will both happen together. Bubbles will simple STOP rising & or a thin layer of clear water will form on the surface of the wet plaster. When either or both happen STOP tapping 'immediately'. You DON'T want to bring all the water to the surface or the plaster will dry unevenly & this will cause the dried plaster to crumble in sections causing worse damage than bubbles would.
(Hold sides & tap firmly for a few seconds)
(Watch for bubbles & or a thin layer of clear water forming)
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