Hermes2020
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This post describes in detail how I make moulds for the realistic elements in my concrete sculptures. As an illustration of the process I will use my bird feeder's right leg, half of which is realistic, and half is an abstract flat slab that extends up and becomes a part of the torso.
The first step is to generate contour lines, similar to those seen on terrain maps. I use Rhino 3D software to do all these operations.
The curves are printed on A0 size paper and pasted onto foam board. The leg does not need high resolution, so I used 10mm foam board. The foot was done separately on 3mm foam board, since the toes needed higher resolution. The final mould was made by joining the leg and foot parts. The many foam board layers were glued together using registration guidelines to ensure precise alignment.
To illustrate my procedure, I will slice the model at the red slicing plane to show a cross section of the layers.
The 10mm steps are obviously not wanted on a realistic element, so some kind of filler paste has to be applied. After some experimentation, I found that tile adhesive has the right properties as well as being quite inexpensive. This image shows how I apply the filler to even out the steps. To show it clearly, I am showing the filler in a gold colour.
Here are some real world photos I took to when I was implementing the above steps. This one shows the leg and foot layers glued together in proper alignment. I can easily achieve a precision of 1 mm in this process. The accuracy is a bit less important that the precision, but is also in the order of 1 mm. As promised, most photos contain a plain white credit card as a scale indicator. The body parts are slightly larger than life size.
Here I am starting to apply the filler, which is an adhesive powder one mixes with water when tiling. I like it to be the consistency of peanut butter. I use soft silicone kitchen spatulas to apply the filler. The key is patience: I build up the walls in a number of applications that are allowed to dry between applications. That way a smooth surface that does not require much sanding is achieved.
As a last coat I apply a layer of very fine textured crack filler to get the final smooth surface. Here the foot and leg are shown with the wooden strips glued on to give a rigid connection.
Finally, I apply at least three coats of gloss varnish to get a finish that does not need any mould release to prevent the concrete from sticking. A disadvantage of this type of mould is that I can only manage one cast from it.
Apologies for this rather long post, but I hope it will be of some interest. I would welcome any suggestions that will help me improve my process. I am aware that it is radically different from the traditional way taught at art schools, but it works for me and does not need expensive silicone moulding products.
The first step is to generate contour lines, similar to those seen on terrain maps. I use Rhino 3D software to do all these operations.
The curves are printed on A0 size paper and pasted onto foam board. The leg does not need high resolution, so I used 10mm foam board. The foot was done separately on 3mm foam board, since the toes needed higher resolution. The final mould was made by joining the leg and foot parts. The many foam board layers were glued together using registration guidelines to ensure precise alignment.
To illustrate my procedure, I will slice the model at the red slicing plane to show a cross section of the layers.
The 10mm steps are obviously not wanted on a realistic element, so some kind of filler paste has to be applied. After some experimentation, I found that tile adhesive has the right properties as well as being quite inexpensive. This image shows how I apply the filler to even out the steps. To show it clearly, I am showing the filler in a gold colour.
Here are some real world photos I took to when I was implementing the above steps. This one shows the leg and foot layers glued together in proper alignment. I can easily achieve a precision of 1 mm in this process. The accuracy is a bit less important that the precision, but is also in the order of 1 mm. As promised, most photos contain a plain white credit card as a scale indicator. The body parts are slightly larger than life size.
Here I am starting to apply the filler, which is an adhesive powder one mixes with water when tiling. I like it to be the consistency of peanut butter. I use soft silicone kitchen spatulas to apply the filler. The key is patience: I build up the walls in a number of applications that are allowed to dry between applications. That way a smooth surface that does not require much sanding is achieved.
As a last coat I apply a layer of very fine textured crack filler to get the final smooth surface. Here the foot and leg are shown with the wooden strips glued on to give a rigid connection.
Finally, I apply at least three coats of gloss varnish to get a finish that does not need any mould release to prevent the concrete from sticking. A disadvantage of this type of mould is that I can only manage one cast from it.
Apologies for this rather long post, but I hope it will be of some interest. I would welcome any suggestions that will help me improve my process. I am aware that it is radically different from the traditional way taught at art schools, but it works for me and does not need expensive silicone moulding products.
. Thank you for taking us through the process and cycle of how you create these fantastic parts, as they have to be perfectly balanced and planned out. The whole thing is so far over my head, that I feel foolish even commenting. 
