Hey I was wondering if any of you could help me with this litte question: I made a mold of a 1/35 scale helmet to cast extra one for a dio I am doing, but I cant seem to get a good casting, it always has air bubbles in it. Is this a common problem with smaller items like helmets? Thanks

Its a common problem with all resin casting. In large subjects there is more 'room' for the bubbles to either work thier way free or you have more freedom to 'tap' them out.
You'll want to tap the mold after you pour it to help the bubble rise to the surface. I don't know if this is true or not but I seem to remember someone somewhere putting a pouring on a washing machine as it spun.
You can also use a toothpick placed across the opening of the resin mixing container as you pour. As the container is on the table the toothpick would be placed parallel to the table across the opening. It would form a diameter across the opening. As you pour the resin will flow down this TP and into the mold. This pouring method helps keep the flow under control and provides fewer bubbles.

On top of what Scoot said, I prefer to mix small quantity of resin inside a syringe and pour it in the mold very slowly with the syringe and a 0.8-1mm needle mounted on it, not smaller otherwise you won't be able to pour the resin out. In this way I've almost solved the air bubbles problem...
Ciao

For larger project or pours, you can mix your resin in a "zip lock" bag, when you are ready to pour snip off the bottom corner of the bag. This allows the bubbles to go to the top while you pour from the bottom.

There's several ways to avoid air bubbles :

1) vacuum the mold when you have poored the resin. This is by far the most efficient procedure, and it gives you crisp, bubble-free results every time. It's what the commercial resin companies do. But a vacuum box is a complicated and expensive thing to make, and it's not something you should do if you're unexperienced.

2) I heard you can also do the other thing : place it in a pressure pot when cast.

Both for 1 and 2, make sure there is a bit of resin "reservoir" on top of the object you try to cast

3) If you want to poor in room pressure conditions, you can avoid bubbles by adapting your mold :
- make sure there is a small reservoir on top of the object
- cut thin air ducts from the top parts of your mold, just to make the air go out. I'll try to make a drawing of that and upload it here. Maybe the silver patch isn't so bad : I have new webspace for pics !!!

Matrix,
I made a step-by-step description to explain how to avoid air bubbles. Feel free to PM me if you have any questions.