Increasing weight of small resin casts

[Halfstory]

Hi
I'm currently making a series of small detailed limited ed. figurines and have just cast the 1st piece from a silicone rubber mould. I'm using polyester resin but as its a small cast 3x3x4" it feels light and disappointingly "cheap" is there a way of increasing the weight of the casts either by adding a filler or using something other than p.resin. I intend 2 finish the pieces with acrylic paint.

Thanks,
Sal

[ahirschman]

I have been using a two part plastic from polytek, called 15-3. They also make one called 15-6. Now they are both plastics, but the 15-3 is highly filled with mineral (rock?) and when cast feels like stone. The 15-6 feels like light toy plastic.

I also recently used a very light plastic, easyflow 60 from polytek. It is very light when finished, but I added bronze powder at about equal proportions by volume. The finished pieces feel, look and weigh about the same as a bronze (OK, a little less, but it is hard to tell).

So, you can probably add just about any thing that is nice and dry, and chemically inert (with plastic). I would consider adding sand, ground stone, ground metals, etc. You could also just buy one of the plastics that come pre-filled.

The instructions for easyflow60 state:

"Fillers can be added to EasyFlo products to vary appearances and densities. Mircroballoons can be dded to create a wood-like, lower density material. Bronze powder, calcium carbonate, fly ash, sand, granite or other stone-like fillers can be added as desired. Usually, fillers should be added after A and B are mixed. It is imperative that any filler be thoroughly dried before mixing with the resin"

In my experience, most additives will work but they should be very dry or foaming will occur. Also, a small test is always a must with any of these chemicals.

Good luck, and let us know what you do.

Ari.

[Arrow]

Lead or steel shot perhaps?

[Merlion]

I've added and mixed talcum powder, marble powder and bronze powder to polyester resin. When bronze powder was added, if I sand the surface, it becomes shinny, a bit like the metal.

By the way, I remember seeing my crazy sculpture classmate adding water and nothing unusual happened. But I am not 100% sure.

[ahirschman]

One thing that I would worry about when adding metal - is that if the metal is too large the expansion and contraction may crack the plastic, so I would keep the additives as Small as possible. I have not experimented with this, so this is only a theory.

Ari.

[Landseer]

Ari is probably right, also, metal pieces, ball bearings etc may sink to the bottom in the liquid and become exposed on the surface.

I have a similar issue with my gothic finial in another thread, it's tall and slender and needs a base, and hydrocal weighs little for this size, so I added a 5/16" thick square flat steel plate painted gloss black, and an oak base under that 1/2" larger so it forms a stepped base as well as adds a couple of pounds to keep it stable.

Is a base of some kind an option?

[OMann]

One way of gaining weight is to use iron filings in the resin when you fill the piece. Iron filings are cheap and are often used with resins, so there shouldn't be any problems with it. I did a course where we were told about this, and if my memory serves me, I think the ration is about 1/1 resin and filler.

I've not filled any pieces with iron but have applied a gel coat with iron which looks pretty neat. Hope that helps!

Regards,
Oli

[Landseer]

Originally Posted by OMann

One way of gaining weight is to use iron filings in the resin when you fill the piece. Iron filings are cheap and are often used with resins, so there shouldn't be any problems with it.

I think one issue to keep in mind with iron filings is the source, if the filings are obtained from a local machine shop or something it could be contaminated with cutting oil and anything else could be in there is if was swept off the floor from around machines.

We cut a fair amount of steel shapes, bars, angles etc but also some aluminum, so it's mixed together and the lighter aluminum might be a problem with wanting to float to the top of any liquid resins I don't know.
We ALWAYS use cutting oil on the steel.

We just sweep the filings off the floor, so they usually have sawdust, paper, dirt, dust and other foreign particles.

[OMann]

The iron filings I've used I've bought from a sculpture specialist - they also sell bronze, brass, aluminium fillers, mainly for use with resins. The iron filings are marketed as a weighting filler. While the bronze filler costs just under £6 for 500g, the iron is under £9 for 5kg.

I'm sure locally sourced filing will be cheaper, but as you said, the purity of it may be a problem. The specialist filler is a very fine powder, which gives an even mix and it can also be used in the gel coat to create cold cast iron figures.

[StudioSL]

Most people use marble filler (bonded marble), and it's the easiest. It's very cheap. I use it on my ten inch figurines and the weight is very nice, but not as heavy as a real bronze. If you go with iron filings, you should make a gelcoat first so no metal actually comes to the surface, or you will get rust. I've done this and it does make a really cool effect. I've also made a gelcoat with bronze powder, which you can buff to a shine, then filled the rest with catalysed sand, aslo very cheap, the the sculpture a pretty darn heavy.

Good luck.