[Brandon]

Hey guys, so I’ve posted about my polyester resin not curing previously, but I’m a tad more experienced now so let me go over a few things.

So I personally prefer working with liquid plastics and epoxy’s, once these are cured the quality of the product is great, durable, and finger prints don’t get embedded in the product.

I however would love to use polyester resin for my plugs because the clarity of polyester resin is definitely greater even by just a bit than epoxy. The image I’ve attached to this question was from a while back, essentially, this is what happens to my polyester resin products after they’ve been man handled and touched etc. This doesn’t happen whatsoever with epoxy and plastic from my experience.

http://oi64.tinypic.com/178zgw.jpg
http://oi67.tinypic.com/21n34mf.jpg

As of recently I tried a new ratio for my plugs, I do about a half ounce of resin and 5 drops of catalyst (the brand of resin is castin’ craft) and it actually hardens much nicer than back then, I wait about 2 hours then demold. However after touching the sides the clarity has already gone down :/

So my question is, what am I doing wrong? Whether the resin is new or old is irrelevant, I’ve never been able to get polyester resin to be stable and stay clean even when brand new. Am I demolding too soon? I read somewhere that polyester resin doesn’t reach it’s full durability/form for 3 weeks! In which case I’d understand why this might be happening. Anyway I’d love to hear what any experienced resin users have to say, thanks!

[Brandon]

I’d also like to note that I now vacuum degass the mixture before pouring into the mold to reduce the most bubbles as possible.

[Katherine Swift]

Are those fingerprints on the side exposed to air while the polyester resin is curing?

[Brandon]

No, only the bottom of the plug is exposed to air when the resin is curing

[Katherine Swift]

Sounds like maybe you need to mix more thoroughly, especially since the resin sounds fully cured.

To salvage the pieces you have, you could try sanding off the surface, starting with a coarse sandpaper, then ending with a 1000 grit or higher. You can then polishing on a buffing wheel with compound to get it shiny again.

[Ron austin]

I just started doing castings for my pen blanks that I turn on the lathe. The ones I did yesterday cured ok. Two that I made today cured out to be a little flexible and on the soft side of hard. I put color dye in it then mekp. Mixed and poured ok. Whats wrong? What did I do wrong?

[Katherine Swift]

What kind/brand of resin did you use?

[Dave]

Hi i have had both problems posted above rons problem for me was mixing too much hardener (would of thought it would have the opposite effect). Brandons is the one i am struggling with all my clear castings are left with finger prints embedded in them from lightish contact holding them just enough to put on jump rings etc never mind just general use i made several keyrings with disastrous effect stuck to pockets or just left with material imprints on them, will make sure i mix the next batch thoroughly as i never thought of this as the other resin non clear, i have no problem with at all except when i mixed in too much hardener and it was more like hard rubber as mentioned earlier any other advice welcome.
thank you Dave

[Katherine Swift]

@Dave, it’s normal for the surface exposed to air during polyester resin curing to remain tacky even after the resin underneath has cured hard. You will either need to sand off the surface or coat with a spray. This is the one I like to use: https://shop.resinobsession.com/collections/tools-and-supplies/products/castin-craft-gloss-resin-sealer-spray

[Dave]

No this is happening to all sides whether exposed to air or not for some reason the clear resin doesn’t seam to harden the same as the other non clear one i use..

[Katherine Swift]

@Dave It may be that you are not mixing it well enough. My rule is to mix it for 10 percent of the pot time while mixing the sides of the cup and stir utensil at least three times during the process.

[Dave]

Thank you for the replies can you tell me the average room temperatures the resin should be mixed at someone said it might be too cold. I live in the uk and wouldn’t of thought it was too cold but right now trying to cover all bases.

[Katherine Swift]

Low 70’s F is what I think works best.

[Fiver Dan]

The marine polyester resins we use in yacht and boat building/repair cures with a tacky surface UNLESS it has wax additive.
Get in touch with a resin/fiberglass distributor with knowledge re: wax additive. Maybe one that deals heavily in the marine industry.
The wax additive in no way negatively affects the strength of the finished product as it ends up in the surface due to the curing reaction but it eliminates tacky surface cure.

[Diver Dan]

There is a company in Dania Beach Florida called Fiberglass Coatings.
They should be able to advise re: wax additives and resins that already have wax additive.

[Katherine Swift]

Yes, those additives work for making the sure the casting is not sticky on the surface exposed to air, but may make your castings cloudy.

[Hamida]

So I made a resin heart shape a few days ago and it turned out beautiful, I tried yesterday and it was a mess. I checked on it today morning, its yellow and full of spots. It doesn’t look at all appealing.. any idea what I did wrong?
The type of resin is polyester resin.

[Macie]

Can I flip the piece over in my mold instead of using the clear coat spray?

[Katherine Swift]

And then do what? I’m not sure where you are going with this.

[Author]

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