"Air bubbles in resin" Topic

Just wondering if there is a 'best way' of reducing air bubbles in resin casting without resorting to a vacuum chamber. Is it possible to pour on piece of the item and then, when almost cured, pour the remainder or just agitate the resin before it goes off to get rid of as many bubbles as possible?

I am using Polyurethane Resin and just wondering if there are any tricks other people have discovered. I can do simple pieces but this one has more small detail but too bulky for metal casting.

Thanks

A vibrator helps. Some people use the washing machine.

Open face mold here, I assume? You can try tapping the mold gently while the resin is still liquid, which may dislodge some bubbles. If there are specific trouble spots (usually corners IME) you can try poking the air out of them with something expendable (eg a popsicle stick), again working while the resin is still liquid.

Is it possible to pour on piece of the item and then, when almost cured, pour the remainder

Most resins will take layered pours all right, but I haven't noticed that they help much with bubbles – and some resins will react badly, causing the layers to seperate rather than cohere. Best to experiment on something small first to be sure.

Polyurethane resins set up fairly quick . Vacuum is best on the rubber , a Pressure pot "crushes bubbles" air back into solution while it set . I have used large and small Pressured paint pots hooked up to a compressor . Some pieces need only a few pounds to knock the bubbles out .
Do not agitate the resin it creates more bubbles . If you do not have access Do it in two stages .
1> mix a small batch , rub it into the details with a gloved finger . let sit until " When she's Jelly she's ready "
2> Close up two part mold and fill .

This was the way we did it before getting pressure pots
Dave Skelley #1 grunt
Altermnative images productions
makers of garage kits

Occasionally for large items that won't fit in my pressure pot I'll do the following:

- Prime the Mold (spray the mold cavity with flat black paint/primer) this step can reduce your mold life depending on what you have used.

- Brush in the detail quickly, but begin your pour before the resin is set.

- Close your mold and use the drop method to pour your resin (thin, steady stream of resin poured from a distance above the mold, 2-3 feet)

Dust the mold with talc. Does wonders for fighting bubbles. I've also dug bubbles out of an open face mold using a tooth pick.

All of the above plus spray a real quickshot or two of mold release at the exposed resin to clear a bunch of the bubbles.

Don't use both talc/baby powder and mold release agent at the same time, whatever you do. One or the other fine, both at once, bad idea.

I have to disagree with Battle Works Studio. I use a low viscosity (80cp) fast cast polyurethane resin (about 180 second pot life) with a wax release and talc dusting. It works very well. The very few bubbles that sometimes occur rise to the surface before the resin "sets up" too much. On most moulds the bubbles burst of their own accord, but sometimes a few at the edges need a little help. Our original resin/rubber supplier recommended talc to help the resin "creep" into the detail. It does work best if the solvent in the release agent is allowed to evaporate fully before dusting, otherwise you can get a gunky talc paste that does not always allow the resin to get into the detail.

Does the wax release help with mold longevity? Does it have any negative effect on paintability of the resin piece? And final question, for if I like the answer to the first two questions: what is the brand of said wax release, and where is it available online?

Thanks!

When I say spray with mold release I don't mean the mold itself. I powder the mold and the open part where the setting resin is exposed there will form a bunch of tiny bubbles as you shake the mold or whatever you do. If you hit those little bubbles with a quick shot of spray release it pops them all and makes the surface very smooth and nice.

Thanks for your comments, the mold is open, for a vehicle with some raised detail. I'll give the 'brush some on and into the detail' first and see what happens. I've mainly used this method for larger items with less detail, this is my first vehicle so willint to try most things.

I might try sprinkling talc on the mold first and see how that works, otherwise will try a toothpick to 'work' the resin into the detail.

Thanks again

In answer to majorplatypus, the release does seem to prolong the mould life. I get 150+ castings from most moulds and lots more from some. I know from talking to others in the trade that some only get a few dozen. I also use a platinum (addition) cure RTV which seems to better stand up to polyurethane. Unlike a silicone release it doesn't seem to affect painting, though resin still needs priming. The brand is Marbo which we get from link in the UK. For the US I think this is the place to go marboamerica.com/.

I could really use some help here. If I wanted to make some casts in Resin of a mini plane that I was working on in say 1/144 scale. What would be the best way for an absolute newbie to go about this? I only want to make 5 or 6 copies but I have seen some many youtube videos etc. on 2 part Resin that I have no idea what a good product is. I'd like a rubber mold that I can poor the resin into (and by the way, would a 2 part mold work for a plane, wings esp?).

A starter kit of some kind is best. It seems with 2 part molds that I need clay, release agent and the resin itself (not to mention making a box to hold it etc).

Again, could really use any advice here.