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As I say, I have never had ANY success with transparent resin, so I take my hat off to you, your efforts look superb. I have found that a good way of dealing with bubbles id to make a rudimentary vacuum chamber using a domestic "Henry" type vacuum cleaner & a large polythene tub or similar. Giving the filled mould a blast in this tends to draw any air bubbles out quite successfully, needless to say, the better the vacuum, the better the result.

As I understand it, clear "glass fibre" type polyester resin needs an oxygen free environment to set without tack & as the silicone moulds are oxygen permeable it always suffers from tack issues.

I look forward to following your progress.

M

Interesting, good thinking, I hadn't actually thought of making a simple vacuum chamber. I was aware of them but thoughts didn't go much further than that will be expensive. I'll give anything a go if it costs next to nothing though. Large plastic tub and a roll of bodging tape, we have some hefty industrial cleaners at work as well.
I had heard/read about sealing the resin from the air during the cure, I wasn't aware silicone was oxygen permeable though, thought the tack issues might be something to do with rapid heat dissipation or alcohols in the silicone and that perhaps the alcohols could be 'cooked out' for want of a better expression.
I tried putting moulds into the oven (without resin in) for four hours. I don't know, it was probably a complete waste of electricity.

One other thing I forgot to mention RE the casting attempts was pre heating the moulds seems to help with the cure. The catalyst resin needs some additional heat (I think), the heat generated by the catalyst during the cure seems to quickly dissipate through the silicone so I recon a little pre heating helps. Don't stick the thing in the oven with resin in though... I tried it to my detriment, it ends in tears as the silicone doesn't like it much.

Hi all
I've recently received a private message from a member on this site who clearly knows a lot more about casting and resins than I do. As already mentioned I did this as an enthusiast, at a hobby level in my home to satisfy my curiosity. Anyway some advice has been offered and thought it right to share some of the details.
Firstly and most importantly please be aware of the possible health and safety risks involved with pouring resins at home. Making a final cure in the home oven is probably/ almost certainly a bad idea and to be done at your own risk and appropriate PPE should be worn. Sorry if some of my humour was a little flippant, a little knowledge is a dangerous thing and all that.
Earlier I mentioned when asked by Mk1 about the resin types that the poly type resin was the more resilient, I think it was actually the other way around with the acrylic being the better of the two, I can't remember for sure. The resin that required a final oven cure was by far the better of the two apart from the slight yellowing.
Sorry for the confusion, I tried another pour a week or so ago but most of the badges were made months ago.
Also I have been advised that making a vacuum chamber using an actual vacuum cleaner and tape is a complete waste of time and will not pull anywhere near the required vacuum needed to de-gas.
That's all
Regards Ollie

A good reasonably cheap way to pull a vacuum (assuming you have good water flow from a tap) is to use a water aspirator. It's basically a tap fitting with a take off that draws a vacuum when water flows through it (at high velocity)

A good reasonably cheap way to pull a vacuum (assuming you have good water flow from a tap) is to use a water aspirator. It's basically a tap fitting with a take off that draws a vacuum when water flows through it (at high velocity)

I remember using them at school.

M

mk1 wrote:
I remember using them at school.

M

back in the 1800's......

EDIT 09/12/2013 ..... these are not the badges someone has just cast (badly) and is selling on ebay.
I made these out of curiosity and not for profit. I have given away some of the badges I cast, I sent these out for free to fellow mini enthusiasts.
I just wanted to set the record straight, I didn't ever intend to make money from this and wouldn't like to think other forum members had seen these ebay badges and assume they came from me.

Ollie78 wrote:EDIT 09/12/2013 ..... these are not the badges someone has just cast (badly) and is selling on ebay.
I made these out of curiosity and not for profit. I have given away some of the badges I cast, I sent these out for free to fellow mini enthusiasts.
I just wanted to set the record straight, I didn't ever intend to make money from this and wouldn't like to think other forum members had seen these ebay badges and assume they came from me.

I've got one of the FOC badges from Ollie.

I haven't tried to apply any paint yet.....seems a shame to potentially ruin a nice casting, but guess I'll have to at some point.

Ollie78, WOW, that work of yours is unreal. I respect the time and effort you've gone to with these.

That's some really nice work. Thanks for sharing your skill with us.

The sort of vacuum venturi tap gubbins you want for filtering solids via a buchener funnel and hirsch flask (at school) is the tool to use. It is better than most mechanical vac pumps you can get off the shelf.