Fabri-Cast 50: Always really brittle? (Now general discussion of resins)

[Zlurpo]

I got some Fabri-Cast 50 from Specialty Resins, and it is super brittle. I mix it in the described 1:1 ration, stir well, and let it cure. It turns white, I wait the allotted time, and de-mold. It is brittle and fragile. Thin bits have no flexibility at all, they just snap. There's no bending to it at all.

Is this normal for this type of resin? It's much weaker than Alumilite.

 

[Zlurpo]

Re: Fabri-Cast 50: Always really brittle? (help!)

Or is there any way to make it more flexible? Any additive that changes it?

 

[robstyle]

Re: Fabri-Cast 50: Always really brittle? (help!)

That would be a question for the manufacturer and not really the reseller.

Resin in general isnt very strong being inherently brittle. Even more so on thin parts. With thin parts you cant really blame the material as you need the proper material for the job. Everyone wants inexpensive materials but you get what you pay for when it comes to quality. Without knowing or seeing the part your trying to cast I cant give any real advice.

 

[bookface]

Re: Fabri-Cast 50: Always really brittle? (help!)

Kind of depends how thin you're trying to go, as well. The lower hardness resins (I'm assuming the '50' part of the name denotes the hardness) are generally slightly more flexible than the harder ones. Like robstyle says, without seeing what you're trying to cast, we're shooting in the dark.

 

[Cosmic Ash]

Re: Fabri-Cast 50: Always really brittle? (help!)

specialty resin is garbage... i usualy get quick cast from tap plastics (same thing as smooth cast 300) and the resin was very bad

i had an amazon gift card i was sitting on for a while so i got a kit from them never again...haha chances are yo have an old or bad batch like i suspect mine was

 

[robn1]

Re: Fabri-Cast 50: Always really brittle? (help!)

They say Fabri-Cast 50 is D75 hardness which is fairly rigid, not really flexible.

How thin is your part? I've made some slush cast parts with Smooth-Cast Onyx from Smooth-On, D80. They are about 1/16 in thick and the Onyx is very tough. I gave the part a good squeeze, it flexed slightly but didn't break.

 

[Zlurpo]

Re: Fabri-Cast 50: Always really brittle? (help!)

They say Fabri-Cast 50 is D75 hardness which is fairly rigid, not really flexible.

How thin is your part? I've made some slush cast parts with Smooth-Cast Onyx from Smooth-On, D80. They are about 1/16 in thick and the Onyx is very tough. I gave the part a good squeeze, it flexed slightly but didn't break.

See, that's how I'd like it to be, and that's pretty much how the Alumilite is. But I couldn't find the alumilite in large quantities. The Fabri-Cast works just fine for solid pieces, but seems lousy for slush casting.

A couple have asked: I'm trying to cast a handle for a tomahawk I'm making. I don't want a solid handle as that's too much resin and weight, so I wanted to slush cast it. But at 1/16" it shatters just getting it out of the mold, at 1/8" it breaks very easily if squeezed/shaken, and at 1/4" it still snaps easily.

 

[Zlurpo]

Re: Fabri-Cast 50: Always really brittle? (help!)

specialty resin is garbage... i usualy get quick cast from tap plastics (same thing as smooth cast 300) and the resin was very bad

i had an amazon gift card i was sitting on for a while so i got a kit from them never again...haha chances are yo have an old or bad batch like i suspect mine was

I was wondering if that could be the case. I'm planning to call them tomorrow to ask about it.

 

[robstyle]

Re: Fabri-Cast 50: Always really brittle? (help!)

Trying to cast a handle like that with a hollow core is doomed to fail with that material. You could back fill it with expanding rigid foam or suspend an armature inside. If using an armature be aware the material will shrink but the armature will not. A number of things from warping to all out cracking and breakage could be the end result.
You need the proper material for the job.

 

[Zlurpo]

Re: Fabri-Cast 50: Always really brittle? (help!)

Trying to cast a handle like that with a hollow core is doomed to fail with that material. You could back fill it with expanding rigid foam or suspend an armature inside. If using an armature be aware the material will shrink but the armature will not. A number of things from warping to all out cracking and breakage could be the end result.
You need the proper material for the job.

The expanding foam is something I was considering, it seems like a good "skeleton" idea. And I'll probly look into getting a better resin. Thanks!

 

[bookface]

Re: Fabri-Cast 50: Always really brittle? (help!)

I've backed small hollow statues with smooth ons 5lb rigid foam. Worked well on those.

 

[robstyle]

Re: Fabri-Cast 50: Always really brittle? (help!)

Just keep in mind different materials will expand/contract and shrink at different rates. This is why resin isnt a good material for this sort of thing. There really isnt any give to it. I use a high impact plastic thats super durable and strong and I wouldnt expect even that to hold up on a rotocast/slushcast hollow handle. You may want to look into fiberglass.

 

[Zlurpo]

Re: Fabri-Cast 50: Always really brittle? (help!)

Update:
It's still quite brittle, obviously. I called Specialty Resins, and while they may not have the best resin in the world, I give customer service two thumbs up. I explained my issue, asking if the resin could have been expired. They guy explained that it's made every couple weeks or so, so it doesn't really have time to go bad. It's just brittle, although it does cure more completely after 24 hours. After explaining that I had expected it to be more like Alumilite, he said that a different one of their resins may be more what I was hoping for, and then told me he was sending me a gallon sample of that type of resin. I call that above and beyond the call of duty, right there.

So we'll see how the new stuff works when it arrives. In the mean time, I did another cast with the brittle stuff, just using more of it. Then I used a can of window sealing expanding foam from the hardware store and filled the inside of it, because nowhere nearby where I live sells the two part pour-able expanding foam.

That worked pretty well. I could likely still snap the handle if I tried, but... I'm not trying! So I made it work, although I don't plan to keep using the Fabri-Cast 50 for slush castings.

 

[robn1]

Re: Fabri-Cast 50: Always really brittle?

That's some great service! I guess they're sending you one of the more flexible types.

 

[bookface]

Re: Fabri-Cast 50: Always really brittle?

That is great service! Another idea just popped into my head, which is that some places (smooth-on is the only one I know off hand) have resins that are very lightweight, that will actually float in water once cured. You could look into doing solid casts with those, as the weight will be more reasonable.

 

[Zlurpo]

Re: Fabri-Cast 50: Always really brittle?

Update: the resin sent to me arrived. I got 2 quarts of Model-Pro resin, and 2 quarts of Color-Pro resin.

The Model-Pro seems to be a great slush casting resin. It spread well, and coated fairly evenly (I didn't even do the pour in, slush around, pour out extra. I just poured in and rotated until it mostly solidified). It's strong and just slightly flexible. Couldn't be happier with it. It's about the color of butter when cured.

The Color-Pro resin cures slightly slower (only about 15 minutes to de-mold though), and it's harder to tell when it's fully cured because it is translucent, and doesn't turn opaque as it cures. It's quite flexible. It's designed to have color added to it (hence the name). I'll very likely keep ordering from them, partly because I like the resin, and partly because the service they offered was quite excellent.

Edit: after curing over night, the Color-Pro is slightly less flexible. No change to the Model-Pro.