Casting Advise please (Im a Newbie)

[chantelle]

Hi!

So Im looking into some projects regarding casting

I want to make some moulds of fish tank ornaments. As most Fish tank ornaments are made from polyresin for example

http://www.petsathome.com/webapp/wcs/st ... decoration
Im looking at these types of things to replicate.







Ive watched about 40 youtube tutorial videos now. I understand some models you can simply tip into your latex mould and leave to set like smaller ornaments.

I understand some things will require two part moulds.

https://www.youtube.com/watch?v=N2yPHzspR90

This video was quite helpful.

Im looking at buying

Polycraft EasyFlo 60 Polyurethane Liquid Plastic Casting Resin 2 Litre Kit

Polycraft GP-3481F RTV Silicone Mould Making Rubber 2.2Kg Kit

EB Silicone Spray

I suppose my questions are, complete newbie questions.

If Im completely honest Im unsure what Im buying, Im looking for a resin that will set and feel like a terrocotta pot, that ornament weight sort of feel? (Im looking for a resin that is that type material)

How far does resin stretch? If I was to make the middle image sculpture at 6inches wide, 4inches long and 6 inches high, would that take a lot of resin?

Im hoping to be able to make reusuable moulds.

How do hollow moulds work? I can not for the life if me get my head around that? Would that be a 2 part mould? Ive made a replica out of playdoh of a boat which is hollow,

What im thinking is, design a box to make replica in. do the bottom half first covering the top half in clay like the video on yourtube does with the shell. so essentiall my boat looks like this (Also making the bottom of the boat open so the latex can be pulled out from inside the cast easier?) So the latex would fill the inside of the boat? Id would just put a big clay blob on the bottom of the boat (Not forgetting my release agent) then fill the box or whatever with latex so it covers the bottom half of my boat (which is essentially upside down) the clay on the bottom to cause the whole will be 2 inches thick so half inch of that will tank outside of the latex mould. (Imagine the yellow is latex (just an inch or so thicker)

So here is the original boat.





here is my replica mould (notice top windows are filled too)

and the bottom where my "clay" would of been (would the clay need to fit the whole bottom?


Then wait for it to dry, flip it the other way, remove clay from top half of the boat and fill the latex box up again?

Basically hoping someone can point me in the right direction of what products to buy and help me with some sort of guideline of how much i need for ornaments of roman ruins and If im even on the right path here lol.

Also if i created caves (bit like a piece of guttering) out of clay can I mould those too?

Thank you in advance

[mangozac]

Hi Chantelle, welcome to RA!

The Polycraft silicone you mention seem just fine for what you want to do. The resin however has far too short a working life. Easyflo 95 would be much better. I will point out however that without pressure/vacuum casting equipment you will end up with air bubbles and the like in your cast parts.

What is your motivation for doing this? Casting such parts will not be a cheap hobby. You can get a rough estimate of the amount of resin required by multiplying the heigh x width x depth of the part (in centimetres) and that will give you an idea of the resin weight in grams. Your sculpture of 4x4x6 inches will be very expensive to reproduce, not only in resin but also in the silicone mould.

The silicone will allow you to cast multiple copies - up to maybe 30 or so depending on the complexity of the mould.

I think your play-do mock up is on the right track. You just need to make sure it's done neatly with clay...

[Fleafa]

I do'n recommend Easyflo 95. Viscous and stays very flexible for a long time after curing.

[RageofAchilles]

You can use fillers, like powdered marble and slate to add weight to the casts, you don't want them to float.

Have you looked into the toxicity of the resins and paint you will use? you don't want to murder all the fish lol

moulds for items of that size will be expensive, your likely looking at 3kg or more for a mould that size also if your looking to sell them you may find you can't produce them cheaply enough to make it worth doing with resin. Maybe a waterproof cement, like the stuff used to self level floors?