Resin not curing.

[Uruk-Hai]

Hello!

I have been casting some resin for a few days. Monday I opened up two cans from Sylmasta. They where roughly two years old since purchase but hadnt been opened.

Was casting during monday and tuesday evening and was going to continue now, but first batch does not harden, and its been three hours? Tried another one in case I made a mistake when mixing but same thing there.

Have placed the resin under a heat source but not much is happening.

Any ideas of what might have happened or/and how to help it?

Cheers
Janne Nilsson

 

[1969]

Janne which resin is it ? if it is clear casting resin that can be difficult to use and difficult to cure if not mixed exactly as stated.

Steve

 

[Uruk-Hai]

Using this one.
https://www.sylmasta.com/product/polycast-g28-polyurethane-casting-resin-2kg/

Strange it appeared over night?

The first one which I mixed four hours ago have become a little bit thicker, not that you can touch it. And it has shrunken quite a bit.
The second I made 2 hours ago start to "muddy" in the bottom.

Cheers
Janne Nilsson

 

[1969]

Shows demould time of 2-3 hours, are you casting at room temperature ?
Also is the resin part a nice clear amber colour, if cloudy them the resin has gone off.

Steve

 

[Tommi]

Did you shake the "A" part, the resin as it has some of the properties of the fluid that settle at the bottom. The G range is normally quite decent stuff but the pot life and de-mould time is quite long for the G28. The G28 is fine if you are Pressure casting of large parts but if you are Vac casting I would use the G26 that has a pot life of 4 mins and de-mould time of 30 mins. What you have could have gone off as it does have a shelf life and depends how old it was when you purchased it. Also curing is dependant on ambient air temperature being within the specs of the resin.

Tommi

 

[Uruk-Hai]

I try giving it a shake tomorrow and see how it develops.
It was slightly colder in the room than yesterday. But it still was 24+ as of 29+ yesterday.

Thanks, mates.
Janne Nilsson

 

[Tommi]

The pot life is about 7 mins for the G28 so it pretty much sounds like it has expired. Like Steve mentioned also check the B part hardener to see if it is clear, if not then this will be a problem.

Tommi

 

[Uruk-Hai]

Hello, Figureteers!

An update. Shook the tins, both of them actually, and behold it worked.

The batch not curing had started to look crystalized and was like sticky breadcrumbs in the mold.
I scoped out as much as I could and then poured another batch of resin. The first cast came out messed up and was scrapped. And it tore some of the silicon from the mold with it.
Second batch was ok with one mold but the other mold had some more pieces torn from it and it started producing lumps in the casts. It can be fixed by modellers but probably would be unfit to sell?

A question of procedure.
Do you guys mix the resin, vacum it, pour it in the mold and vacum it when in mold? Or you just pour it in the mold and then vacum it?

Also, what do you use to clean tools with from both unmixed parts?

Cheers
Janne Nilsson

 

[1969]

I pour resin into moulds then vacuum, let it bubble up for a little while then slowly open valve to return chamber to normal pressure then vacuum again. You will need to create a reservoir at the top of the mould to contain the resin that will bubble out, I use brown packing tape wrapped around the top of the mould. Should get pretty much bubble free castings if sprues are done correctly and you vacuum twice. I use fast set resin so all this has to be done within about 2 minutes but with practice it can be done even on large items.

I normally just wipe tools with kitchen roll when resin is still wet which is enough to keep tools clean.

Cheers
Steve

 

[Tommi]

Mix , pour then vac. Let the air back in slowly so as not to pull back any of the surface bubbles back into the mould. I always like to make a deep pouring reservoir to help with this.

Tommi