Clear Resin Casting - Degassing Problem

[Joy]

New member here, with a question for the more experienced.

I'm working on a small part of a larger batch of replicas for someone, a tear shaped crystal from Final Fantasy 13, and I ran into a problem in the casting process.

This resin is not degassing as it should (it advertizes high self-degassing). I'm still a low-end propmaker, and lack a vacuum chamber, nor can I really afford one now. Is there anything I can do to minimize these cursed bubbles? Or is there another clear resin that works better than this cheap mess that doesn't require I have a crazy ventillation system?

What's being used:
Easy Cast clear epoxy
Castincraft transparent dye
Rebound 25 Silicon mold, with a pour channel and a vent channel

 

[who45]

i found when using a certain make the bubbles were caused by the heat of the 2 chemicals mixing and there was no escape for them in the mold in the time easy flo set - so the bubbles had only one way to go....which was up until they hit the wall of the mold and couldnt release anywhere - i ended up going for a water clear resin by another maker - took 12 hrs to harden but it did so bubble free

easy cast clear was what gave me the same results as your having

in the end i opted for this:
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=220432712155

i got clear casts from silicone molds with the replacement product but the trade off was a longer drying time

 

[who45]

this was the one i used instead of the easy flo:

this was my easy flo prob - apart from it not being water clear which was my mistake :

 

[Joy]

That stuff does look excellent. Do you know of any vendors that will ship to the US though?

 

[fettster]

If you have a decent Air compressor, you can get a pressure pot quite cheaply and pressure cast the resin.

Or you can warm each components separatly to reduce the viscosity on the resin to allow the bubbles to rise quicker although doing this will also speed up the cure so it can be hit and miss

 

[Superkrates]

If it's not being caused by a reaction within the resin you can use an irrigation syringe to inject it into the mold (opposite end of vent). Rather than making the bubble rise to the top of the liquid, the liquid's ceiling naturally lowers to meet (and purge) the bubbles as the resin is drawn into the syringe.

 

[who45]

i tried all combos with easy flow - even to the degree of a high pour with a thin line - in the end as it happened every time i put it down to a chemical reaction and the fact the easy flo went off very quick - too quick for the bubbles to escape - the replacement i used smelt more like resin should (very strong) - easy flo doesnt have that resin smell.

i would think a resin that didnt go off within a couple of minutes from mixing is more what you need to give the product time to release its bubble

mine i think is aimed more at glass fibre products, as i did try another modelling resin which after 24 hours was still like jelly - that was aimed at creating water effects tho and was useless for casting

 

[who45]

Water Clear Polyester Silmar 41 Casting Resin | eBay

this is all i saw on ebay.com - the keywords looked similar to mine

 

[juno]

Joy, have you tried Smooth-ons new clear castable epoxies? I believe they don't need a pressure pot. EpoxAcast® 690 Clear Casting Epoxy Resin Product Information

 

[BlindSquirrel]

That looks promising! Have you tried it, Juno? I'd love to have an alternate to that crap EasyFlo.

 

[zorg]

This resin is not degassing as it should (it advertizes high self-degassing).

from looking at the pix it doesn't look like you are giving the gas a chance to go anywhere:unsure

the second pic shows the bubbles are at the top half of your cast so it shows the gas was trying to "get out" but couldn't.

its locked inside your mold. if you had an open mold the gas would rise to the top and burst at the surface. this is what they refer to as self degassing.

cut the manufacturer some slack, they are not magicians.


-z

 

[exoray]

from looking at the pix it doesn't look like you are giving the gas a chance to go anywhere:unsure

I have to agree with this, you have to make the vent the highest point so gas can rise up it, if you want it to self degas...

Cast it similar to this... You fill from the bottom, so you are not 'pushing' air down into the piece and trapping it, but instead driving it upwards as you fill the part towards the vent, the vent is at the highest point and any rising air should funnel towards the vent, if there are other 'high' places you need additional vents...

And to be honest the pressure tank is 100% worth the investment if you plan to continue with clear resins... Also a mold like the above works well under pressure as it has a 'reserve' in the vent and fill that will replace any lost volume in the part being cast while under pressure...

 

[greatsaje]

I have found with most clear resigns you need to :-
- preheat the 2 parts in some hot water
- work in an environment between 24c(75f) and 30c (air conditioning helps)
- it need to be mixed for 2 min in one cup nad the poured into another and stired for another min, what you get is a very bubbly mix
- when i do single side molds ie no back I pass a bbq lighter over it an instantly kills all bubbles
- I havn't attempted it myself but you could try an keep the mold heated above 24c(75f) to aid in the bubbles escap for about 5 min.

Hope that helps, it took me about a litre of mix over 2 weeks to get my tecnique right.