Re: Polyester Casting Question


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Posted by bruce paul fink on March 13, 19100 at 12:21:23:

In Reply to: Polyester Casting Question posted by Eric on March 13, 19100 at 11:35:20:


Polytek products, catalogs and instruction classes (and I assume tapes) cover the whole area of industrial to sculptural to controlled machine part casting and replication so I would certainly trust them. Even their $10. catalog (which has a refundable price with a first order as well as I think a 15 or 20% discount ... first order only) is well worth the price and is very informative but of course on a lesser level.

As for the casting resin info, their catalog is highly detailed in systems and ways to use the products they sell. They have even recommended other distributors on occasion when they do not handle what you might be looking for. You probably want a water

clear type from the way it sounds. The less clear types are cheaper but unless that doesn't mater stick to the water clear. Cure times and room temperatures are very important, don't ad lib there and be very accurate with the catalyst measure.

I basically use a semi clear base polyester resin that is the same as used for boats and lamination lay-ups. Can be gotten at any Auto Supply Outlet for body patching and I get the type NOT filled with chopped fibers or clay fillers. It goes for about $12 to $20 per gallon there... (I get it by the cheaper 55 gallon drum and use about 2 to 3 drums per year).

Here are some other thoughts:

The syrup like resin is then the main binding vehicle and you can start to mix 'stuff' with it to make the body of the mix much thicker,

to color it,

and to give it more strength.

Use cheap stuff and get a cheap looking result, mix quality stuff and you can get an exceptional end product.

This 'stuff' must be either fully dry or at least compatible to the resin.

Some examples:

for models that are not necessarily the finished end I use microballons as a filler to make it a hard foam, or fine sawdust to make it a wood patching filler.

For a more permanent and durable end:

baked dry sands,

granular marble sand,

silica sand or fine silica flour,

iron fillings or bronze fillings or any metal powder but do make sure that it is fairly clean stuff and not covered with oils or stuff left over from the sources that made it.

I douse a can of these metal chips in a solution of lacquer thinner and then drain it off and spread it out and dry it... does a quick and good cleaning. Get it for free this

way, or you can pay $7 to $25 per lb to others to buy it....but not in this guy's budget,

for strength: chopped glass fibers (like 1/4 inch),

chopped nylon thread fibers, etc.

for coloring: any of the dyes specified for the resin OR,

lacquer based paints in small quantities,

or powdered concrete colorants such as earth colors,

or lamp black,

or powdered tempera type pigments, etc.

for thickening ( so it can be puttied up a large mold wall):

either a fumed silica (which I do not like but works... too dusty),

or the fiber filler that Polytek sells and looks like loose paper mache fiber but is nearly

invisible when mixed in (my preference).

Get the idea? Of course do testing on any new trials of mixes.

AND OF COURSE do mix in the catalyst which will make it all set up and harden in your determined time frame,

or will make you cuss it all out if you don't mix it in well,

or add too much and have it set up as you stir it,

or make a great stink if you do not ventilate...

this is about a 1 to 2% mix depending on the other ingredients you have added. Best here is experience and tests.

A HEALTH NOTE HERE... while the resin stinks when liquid, it is not that bad for your health...(I didn't say good, just not that bad unless you are allergic to it).

The Methyl Ethyl Ketone Peroxide Catalyst however does not smell that strong but is VERY BAD. Obviously a need for good ventilation or outdoor casting.

So what is the finished material like?

Not the cheap / plastic Corrian look of those common sink top casts unless you do it that way... but can be more of a stone, or other look of it's own.

As for durability outdoors:

This depends on many things but it can be quite exceptional. The thing that slowly destroys the clear polyester resin binder is ultraviolet light. You can conquer that problem if the material has any halting additive to slow or stop it. Coloring does that in many cases. The fillers also do it. There are also CLEAR ultraviolet absorbers that work. (And they really do work... see any cosmetic ad since that is the basis of sunscreen and you certainly don't see that enough to wonder what is on top your head (hey I'm balding so that's where I use it).

Polyester resin / fiberglass media has been deemed too permanent for grave caskets since it will supposedly not break down if buried for 15, 000 yr.??? how do they know that? got me.

I started experimenting with this back about 1955 in the form of custom motorcycle fenders and then started mixing steel fillings with the resin for cast sculpture bases.

Years later I realized that it was more permanent than the steel sculpture mounted on top (which could rust outside).

It is the resin that coats each particle of steel grain that helps it to not rust any further...

same with marble which now becomes acid rain resistant...

same with bronze fillers which do not continue to patina age as fast once the metal

grains are coated...

Also slows down any electrochemical decomposition of differing metals ...

Also has a differing temperature transfer so when aa form is in the heat of the winter

sun with the ice and snow still on the other side it can take the shock with no apparent

aging effect...

Some stuff huh?

I am in he process of casting a tombstone right now for a student that is fully alive and wants one in this material as it can also house a glass container for the ashes and then be resealed with more of the media after it was filled. It was her idea but certainly seems sensible to me not being one to want to hang around in space much once the transfer arrives. Don't get me going.

Hope this helps some. Get the catalog for more specific details.


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