Casting help/tip to avoid air-pocket by pour hole/spout?

[xl97]

First time I made a mold...

these are my first casting attempts.

Mold: *(long story) but the quick and dirty is, 2-piece mold, (Alumilite RTV for bottom and Alumilite High Strength 3 Flexible for the cover/top)

I made a hole on top so I could pour in my resin, and cast a few.

I know the smaller bubbles are from pouring to fast or mixing to fast...etc.. (and even better would be the pressure pot or whatever it is called)... but those are more 'cosmetic' at this point.. and are not a huge concern.

but I am talking more so about the 'huge' air-pocket right where my funnel is to pour in the resin (as seen below in the pics)

Are there any tips/tricks that can be to avoid this? (it doesnt have long time to sit after mixing the parts.. so I need to pour 'relatively' quickly)

I tried tipping the mold toward the funnel, so the air would escape.. but it does seem to be doing so! LOL

All suggestions are appreciated.. thanks!

 

[ZeroSum]

You'll need a vent for that air to escape from as the resin fills the space.

 

[xl97]

ZeroSum

thanks for the reply...

I have another hole for the 'air'.. it fills (you can see there are 2 little 'nubs') one if from the 'funnel/pour' hole.. the other is just a regular 'hole'..

Am I pouring too fast? do I need tilt more? or a special way? I'm hoping to have another 'go' tonight/this weekend... but really dont know what to do different to stop this from happening?

 

[HighlanderFX]

It could be the location/size of your nubs. Try tapping the mold once you've poured the resin in to release the huge air pocket into one of the nubs. You can also give the mold a very gentle "squeeze" to force out the air pocket if you don't think the tapping worked. You might have to top it off with resin if you squeeze too much.

 

[xl97]

HighlanderFX - thanks for the reply!!!

ok...

I'll give it a try (bump/tap)


So:

* bump/tap (not much time to do this) lol
* leave air 'hole' open

I'm picking up some more resin in the the hour.. so I can 'try again'

This is my first time every doing anything mold/cast related.. and I'm kind of in 'awe' a bit.. I really enjoy the process (cause it new.. and not 'work' yet).. and getting a result from the mold.

It crazy it says the demold time is like 10 minutes???

 

[VashDstampede]

For flat back pieces like this, you can make the pour hole a lot larger, in fact it can span almost the whole size of the piece (that is of course if you don’t need that center indent).
Just don’t pour too high so there won’t be too much sanding needed for the cast.
Always tap the mold a few times after pouring the resin to raise the air bubbles to the top.
If you have a small brûlée torch, you can also do some quick passes on the resin, before it kicks, to pop some of the smaller air bubbles.