Casting problems

[dai sensei]

Ok two separate problems:

1. The pressure pot condenses moisture and the moulds end up covered in water :~ - Is this common, and do I need to make a roof of sorts to guide the moisture build-up away from the casting bed?


2. I didn't use enough catalyst in the first mix :doh:, this combined with the moisture from the above meant I have a sticky chewy brew :((. Three days and spraying with catalyst has helped, but seems a long way off before it's going to set :(. If it was just a resin cast I would throw them away and start again, but these are worthless wood blanks with conkerberry, so I would prefer to save them. I was thinking of throwing it all in the oven to cook them :v:.
Any ideas to help?


Thanks in advance.

[Big Shed]

1 Sounds to me as though you have a moisture problem in your compressor air supply. This sometimes happens when you haven't drained your tank of water for a while, and/or you haven't drained your water trap. (You do have a water trap I assume?)

2 Spraying with catalyst will only help the outside of the resin to cure, not right through.
I would put these blanks in a toaster oven, not one you are going to put food in again. Seeing that it is a wood/resin combo, you need to keep the temperature lower than for resin only. I would suggest 70C, no higher. My guess is you will be looking at least an hour at this temperature, maybe longer.

PR and water are not good friends, so try and keep them apart. Your climate of course doesn't help and would have contributed. As the air is compressed the after is condensed out, hence the need for regular draining of the compressor tank and the water trap.

On some compressor systems I have had 2 or more water traps, if the air line is long it is often a good idea, if not mandatory, to have an extra water trap at the end of the line, just before the point where the air gets used.

On catalyst quantities, for casting thin sections such as ribbons, and also worhtless wood where there is less mass of resin you need to increase the amount of catalyst as there is less heat being created by the thinner resin sections. Probably double what you normally use.
I normalyy use 1ml per 100gr of resin, for ribbons and worthless wood I use 2ml.

[dai sensei]

Thanks Fred. I have a water trap on the compressor, but the line goes around the shed then into a wind-up return hose, so perhaps I should have another water trap at the pot.

I know I didn't even use the standard amount of catalyst, probably 0.5ml to 100gr :-. I can understand your theory on the catalyst, so will try using even more than normal next time, heaps more than this time :B.

Lucky I asked, I hadn't thought the resin may have a low melt point. Don't have a toaster over, so might try the normal oven as low as it can go with the mould between 2 old cake tins. I'll leave it until the weekend, hopefully it will also harden up a bit more by then.

[NewLondon88]

Neil, I wouldn't use the regular oven.. EVER! You're going to be putting food in there
(I assume) and it isn't a good idea to mix the two.

I'm not sure about Australia, but in the states you can pick up a new toaster oven
for about $20. At yard sales, they go for a dollar.

Once you put resin in them, never use them for food again.

But PR will set with heat alone, the catalyst is simply a convenient way to get the
heat you need for a cure. I set my toaster oven on 'Warm' which is about 150F or so.
An hour in there and most everything is fine. However, it won't cure improperly mixed
Alumilite .. nothing will! But the oven will cure PR that has no catalyst added at all..
PR is pre-catalyzed, so heat alone will do it in a pinch..

[dai sensei]

Although I too would prefer not to use the oven, I'm not sure there would be a problem. Keeping it away from the flame, heat low and within metal cake tins there is little or no risk of fire.

Is it the resin/silicon and possible associated fumes ?

Not sure about a toaster oven as the mould may be too big and element too close to silicon mould. They are still in the mould as I'm worried about removing the blanks and they fall apart in the process (7 blanks).

I might check out what sort of toaster ovens I can get around at secondhand stores.

[Big Shed]

Neil, I would not put any item containing styrene and MEKP into any item or appliance that was ever going to be used with food again.

Not only do your blanks contain MEKP, you have "sprayed" extra on it.

I would also not expose this "witches brew" to naked flame, nor would I do any of this inside any part of my house, least of all the kitchen.

Please read any MSDS for MEKP (http://www.eagerplastics.com/mekp.htm) and see what sort of chemical you are dealing with.

I think you need to treat this stuff with the respect it deserves.

[NewLondon88]

I still wouldn't get it near an oven you'll ever use for food again.
PR contains styrene (vinylbenzene) which is carcinogenic and can cause
respiratory problem as well as damage to the central nervous system.
It also produces carbon monoxide when heated.
Vapor is explosive when exposed to heat or flame; reacts with oxygen above 40C
to form a heat-sensitive explosive peroxide

I wouldn't want it in a living area till it's fully cured.

http://msds.chem.ox.ac.uk/ST/styrene.html

[dai sensei]

Ok I've got the hint :rolleyes:

Today I had a bit of time between meetings so called in to the recycling centre and they had a toaster over for $8, two elements and a timer, works well :2tsup:. I also got a water trap/gauge from Supercheap autos (not that cheap), then a brass standpipe with threaded ends from the demolishing yard for $2 so I could mount it above the pot. The standpipe was a bit longer than I wanted, but it worked well and had the perfect threads for the fittings I already had.

When I got home the casts were still sticky, but firm enough to take out of the mould, so I took them out and cooked them :p. The oven stickers said top element 160 degrees, bottom element 200 degrees, and both 280 degrees. So I put them in with top on only for 5 mins, left them for 20mins, then on again for another 5 mins. It works :2tsup: Turned them over and recooked the other side to make sure.

Put together the piping and ran the pot - yes that worked too, no water :2tsup: Since I emptied the casting mould, I couldn't resist loading up another set of worthless wood blanks. This time Budgeroo root pieces in silver and copper resin. They are setting now, with a lot more catalyst :rolleyes:.

Thanks for the help guys, problems solved :2tsup:

[dai sensei]

I cleaned up the blanks today and finished one pen. The pen blanks photo shows the true colour as it was taken in the sun, the pen shots are in the tent.

Hope you agree, they were worth saving.

[dj_pnevans]

Neil yes it was worth it. Well done it is good when you learn from when some thing goes wrong.
David

[NewLondon88]

ah.. definitely worth it.. They look great!

[Sawdust Maker]

Yep, I agree
lookin good :2tsup:

[MBUMIK]

:2tsup:they look great well done on perservering:2tsup:

MIK

[dai sensei]

I did another cast of Budgeroo, half with copper resin, the other half silver. Photos are as they came out of the pot, then after cutting/sanding to shape :cool:

I already have a few glued up to turn, can't wait until I see what they turn out like.

[Dorno]

looks can be decieving. I bet when you make the pens they turn out teriffic. I can't wait to see your finished products be sure to show them to us.

Cheers Ian

[MBUMIK]

is that one piece of wood in the casts or is it multiple pieces with resin poured over the top????:think:

did you use vacuum or pressure or both???:think:

i know i ask a lot of questions:bricks:

they look interesting, i know the finished product looks like wow:2tsup: