The Ship Model Forum

I am trying different casting resins looking for the right one for my needs. I'm casting tiny little fittings and I've found that the easiest way to avoid bubbles is to "chase" them out with a piece of tiny brass rod. This works extremely well except the resin starts to set up before I can pour many pieces. Very wasteful. To avoid this I've been shopping for longer setting resins. Polytek Easyflo 95 seemed a great solution until I tried it. The stuff lasts long enough to play with while liquid, but it sets soft (at least for tiny parts - I haven't tried larger pours). Has anyone else seen this? I know Polytek is a featured advertiser on this forum, so I'm hoping I can find someone with experience using it.

Can anyone recommend a longer (~5 minute) setting resin good for small parts?

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dave

Time flies like an arrow. Fruit flies like a banana...
Groucho Marx

I'd go with Smooth-On Smooth Cast 310:

http://www.smooth-on.com/Smooth-Cast=-3 ... index.html

Says a pot life of 20 Min, but I get closer to 8 out of it before it starts to set up.

Another option would be to use graduated syringes to accurately measure smaller portions of resin for small batches and less waste. I picked up 50 of them on ebay a couple years back for a few bucks. Keep the "A" and "B" apart and they'll last quite a while.

Something like this: http://cgi.ebay.com/180687394837

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-- Scott

Cold resin also sets up slower- keep it cool/chilled.

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Sean Hert

Thank you for the replies. The Smooth-on product does sound promising - now I need to figure out what to do with 3 pounds of casting resin I can't use! Maybe take a life-mold of the cat? (that should be an interesting experience!)

The syringe idea is inspired. Definitely looking into that.

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dave

Time flies like an arrow. Fruit flies like a banana...
Groucho Marx

The Easyflo 95 will work, however the demolding time will be greatly extended.
But they will cure hard. In the summer heat, I prefer easyflo 95.

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. http://modelsminiatures.com/model-boat-fittings/

I don't mind the demold time - the package suggests 24 hours and I'm cool with that. I cast some *very* small parts perhaps 3 months ago. To date they are still soft and pliable. Filing, sanding and machining are out of the question. I will say they are absolutely the most accurate castings I've ever done, but they are not usable. Frustrating.
Is there something I might be doing wrong to prevent hardening? I'm being extremely careful in ratios during mixing.

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dave

Time flies like an arrow. Fruit flies like a banana...
Groucho Marx

Have you tried putting talc in the mold, shaking most of it out, then pouring in the resin? The talc will draw the resin closer to the rubber and this will eliminate many (if not most) bubbles and voids.

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If you haven't used the easyflo product in a while, then the "B" side needs to be shaken.
This is common to all two part resins. Typically the "B" side will separate and settle over 24 hours, and
the bottle needs to be shaken before measuring and pouring. It is a little annoying, because you entrain a lot
of air bubbles, but if it is left for a few minutes after shaking, then it is usually fine for mixing.

Not shaking the "B" side of the polytek product before use, will definitly lead to "gummy" or rubbery parts.

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. http://modelsminiatures.com/model-boat-fittings/

Now *that's* a clue. I'll try that. Thanks.

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dave

Time flies like an arrow. Fruit flies like a banana...
Groucho Marx

Okay, I've cast a few new parts after shaking the bejezus out of the resin first. Wow, what a difference!

I was concerned after spending mondo bucks (for me) on large bottles of resin I apparently couldn't use. Now I can use it. Thanks!

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dave

Time flies like an arrow. Fruit flies like a banana...
Groucho Marx

Good to hear...

Well sort of... I was hoping to buy the rest of your "95" at half price...

So now that this is working out, do we get to see two turbines, and
a full hull section through the Lusitania engine room?

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. http://modelsminiatures.com/model-boat-fittings/

The project has morphed a little. I want to show the engine room cutaway and the Gunze 1/350 Lusitania full ship on the same base. That should give the viewer a little context. I've been giving my time to the full ship - perhaps I should start a thread here to document the build... it was an auxillary cruiser, after all.

You make me think I should spend more time on the engine room. It's been awhile since the last post!

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dave

Time flies like an arrow. Fruit flies like a banana...
Groucho Marx