A mishmash of questions....

[CLA001]

Hi all,

Well I've read through the library and many posts on the forums and I have found them all really quite informative. Unfortunately in a way I seem to have absorbed so much information I have ground to a halt. So I thought I'd try and phrase some of the questions in my mind to see if I can get an definitive answer. So apologies for causing duplications etc. but I really am getting a little confused.

1. I "thought" to get air out of Acrylic blanks - you used a vacuum chamber. Now after reading various posts here I find people talking about both vacuum and pressure chambers. Which should I use - does it make any difference. (as stated in my intro. my self built vacuum chamber has met with limited and sticky success). Is there a difference, what's the pros and cons etc.? Library seems to cover both approaches?
(Nb. I have a compressor which may be a better tool (for pressure) than my reclaimed fridge compressor being used as a vacuum pump?)

2. When using the previously mentioned vacuum chamber I had several successful test castings that were completely clear (i.e. had put no colouring in them as I was testing for bubbles and they came out like glass). I finished one tin of resin went to another and using same ratios (and same type of resin) the next batch came out looking like honeycomb. (quite fetching in its own way but not what I was after). I am pretty certain that if anything the vacuum chamber seemed to put more bubbles in than when I started. Later casting tests from same batch have not been so bad - but definitely seem to deliver more bubbles than my other batch of resin. Can it go off? Should I be taking special storing precautions?

3. One for the Anglophiles... loads of information about where to buy things (I "wish" we had this mythical nirvana called Harbour Freight in the UK) but does anyone have any good sources for "stuff" based over this side of the pond at all?

4. Due to my frankly huge backwards progress using the next tin of resin (This and the previous resin is the type that uses the 1% of MKEP(?) catalyst). I bought some of the 50/50 resin that requires you to mix the 2 components in equal volumes. Not only was this expensive but although advertised as clear it isn't - turns out a yellowy kind of icky colour. And still seemed to have bubbles even after a 60min dose in the vacuum chamber. Can someone give me the "best" type of resin to use and ideally where I can get it over here?

(Sorry about lack of details - recently had operation on the knee and the shed seems a long way away to get brands and types of resin at the moment).

I think that's about it - in essence everyone else seems to find no problems with this while I seem to be moving slowly ever backwards.

Any help much appreciated sorry If I've not been concise enough I will endeavour to provide more details if needed. I have more questions but I think these are my basic fundamentals at the moment.

Regards
Clive

 

[Kenny Durrant]

I think one reason you might be confused is that there are several different people that cast and stabilize and there are probably just as many different techniques. That doesn't mean some are wrong or necessarily better but thats works best for the person doing the prosess. I use a vacuume only for stabilizing and a toaster oven for casting and thats it. I only use Polyester Resin for casting. I also only cast embedded objects and haven't tried making solid P.R.Blanks. Some use pressure for both Alumilite and P.R. I would say when you research make sure to keep things seperate or things would tend to run together, at least for me. Don't give up because it's just as much fun as turning and just as addicting.

 

[walshjp17]

While I cannot answer any of the casting/stabilizing questions -- just getting started myself -- I do have an answer for the Harbor Freight query:

Look at Machine Mart ==> www.machinemart.co.uk. They also have 60+ retail outlets in the UK.

Their adverts in Woodturning magazine are eerily similar to HF's and their prices seem comparable $ on ￡.

 

[Jim Burr]

As discussed weekly...use either, neither, vibrate and or warm...the choice is entirely yours.

 

[mredburn]

There are two main factions in casting on this side of the pond the Silmar41 type polyester resin that uses mpek. NO vacuuming or pressure is needed but vibration does help remove any trapped bubble. You can use pressure if you want to .

The other is Alumilite which is a 2 part mixture and Pressure is needed to compress the bubbles as they off gas during curing. Usually 40psi is enough although some go higher. You need to clarify water clear when buying 2 part epoxy resin types.

 

[CLA001]

Thanks all for the replies, though the note on Machinemart is I'm sure, going to wind up being expensive ;O)

And thanks very much for the clear summary of the different types and how to prep them, just what I was looking for a clean general guideline.

I think ill look for a pressure vessel I can run off my compressor as i'm not really happy with my homemade vacuum chamber.

Thanks all much appreciated.
Regards
Clive

 

[steve worcester]

For acrylic (I use Alumilite) and pressure cast. No Harbor Freight, try eBay looking for paint pressure pots.

The yellow cast may have been an old or previously opened resin. They definitely oxidize, at least the A side of Alumilite does.