Speaking of Resin....a few questions.

[Shawn R. L.]

Some of the stuff I have done has been cast in odorless resin. While I can\'t SMELL it, is it still giving off nasty gasses, just you can\'t smell them? I\'m told this is the case with odorless turpentine.

Also, I\'ve wondered if anyone has any knowlege or hands on experience with using static charges during pouring. Maybe charging the mold release powder or some sort of fan that would charge air being blown into the mold. My hope is to help eliminat some of the \'void\'s\' that can happen during pouring- not bubbles per-se but the areas that the resin just won\'t go into, especially the little details.

 

[airhead]

Shawn, the only way I know of to reduce voids is to use slower cure resin and a vacuum chamber.

Pour the part. Put mold and part in vac chamber. Pull vacuum. The bubbles get very big, expand and come to the surface (hopefully).

Then release the vacuum and the small remaining bubbles collapse.

That is how it is supposed to work in theory.

 

[Shawn R. L.]

Yeah, at Armorcast they do, I think, both. They vac it to get them out, then pressurise it to smash the remainder.

It\'s improving the acual flow I\'m concerned with. I\'ve wondered about some sort of ultrasonic vibrator.......yeah, yeah, jokes will probably follow...

 

[wiccanpony]

Originally posted by Shawn R. L.
Yeah, at Armorcast they do, I think, both. They vac it to get them out, then pressurise it to smash the remainder.

It\'s improving the acual flow I\'m concerned with. I\'ve wondered about some sort of ultrasonic vibrator.......yeah, yeah, jokes will probably follow...

ok why is everyone looking at Me?

:twisted::twisted::twisted::twisted::twisted::twisted:

 

[Sand Rat]

Was going to suggest the same Shawn - I know it works for casting with plasters.

Not sure if it would work with resin, but it should.

Jeff may know for sure.

 

[airhead]

Originally posted by Shawn R. L.
Yeah, at Armorcast they do, I think, both. They vac it to get them out, then pressurise it to smash the remainder.

It\'s improving the acual flow I\'m concerned with. I\'ve wondered about some sort of ultrasonic vibrator.......yeah, yeah, jokes will probably follow...

Hirst Arts has a set of plans for a cheap vibrating table to do their plaster casting on. If I recall:
Quarter sheet of plywood
Electric sander
odds & ends. (rubber feet, clamps, etc.)

 

[Einion]

Originally posted by Shawn R. L.
Some of the stuff I have done has been cast in odorless resin. While I can\'t SMELL it, is it still giving off nasty gasses just you can\'t smell them?

You\'d have to check to be sure. But at a guess it\'s giving off less VOCs, so it\'s not tricking you into taking less precautions by smelling less, only to be poisoning you quietly while you don\'t notice.

Originally posted by Shawn R. L.
I\'m told this is the case with odorless turpentine.

Whoever told you that, or whatever source you read it in, is incorrect, or at least very misleading.

I hate to say how often over the years I\'ve seen this on various fora and some people just don\'t buy the reality but I assure you it\'s correct. Yes, low-odour solvents / OMS ( \'odourless\' mineral spirits) do have less smell because there\'s less smelly stuff in there, but they also give off less vapour because for this type of thing smelly basically equals volatile, or easily evaporated.

So in short: less vapour and the vapour is less toxic.

The way to check to be sure is to look at the MSDS for numbers like the PEL (permitted exposure level) and TWA, see here.

As far as voids go, degassing the resin is a big first step (as is using a low-vis resin in the first place of course) but pressure casting is the way to fix it from what I\'ve heard, which is why it\'s relied on commercially where detail is important.

I\'ve also read that parts placement/orientation and mould design help hugely in minimising the problem.

Einion

 

[mickc22]

you vacuum the silicone when making the mould, and you pressurise the resin when casting

this is the place to ask:

http://groups.yahoo.com/group/casting/

 

[Shawn R. L.]

Thanks all.

 

[DarkStar]

This tutorial here from Dan Perez: Two Stage

Covers DIY approach to pressureless casting using the two stage pour technique, mainly directed at those without the use of a pressure casting system who want to try and avoid tricky spots where voids can occur. Lot of other great info as well on the other pages for proper mold making, sprueing and setting everything all up for a good cast.


Scroll down until you see \"Problem Areas\" in red on a pic, is where he gets into two stage pouring.

 

[Dragonsreach]

A while ago I saw a TV demonstration of pouring Resin into a mould where the pourer used a stick to pour down to reduce the amount of Air Bubbles.
Don\'t know it that\'d help you but it seemed to work for them.

 

[Dragon Forge Design]

with out seeing your molds and where your voids are my only guess is they are voids or internal cavities that rise up in your molds..

If your using a 2 part mold and pouring into a hole to fill, fil the mold with resin. cover te hole and rotate it around 360 to try to allow that trapped air bubble out and fill your void.

Also using a disposable plastic syringe to inject the resin helps force out the air. you can buy them cheap on eBay.

Vibration will only add more bubbles.

also try talcing the mold to help release air bubbles.

But with out pressure casting its hard to eliminate bubbles.

Also the vapors that its giving off that you mention are similar to those that CA glues give off. They are heavier than air so they go to the floor and can build up over time.

Resins like Smoothcast 300 are NOT carcinogenic though.

 

[Sand Rat]

I told you Jeff would know.