If so looking for some advice,

Looking to cast a fairly large piece (1.5m by 0.25m by 0.04m (4cm) deep)

Have been looking at polyester cast resin and polyurethane cast resin. as seem the best fit. But anything else to look at?
Has to be hard and dry/touchable on finish. Will be tinted so doesn’t need to be perfectly clear.

TIA

I work in the PU industry.
I would go with a PU at the size you are wanting to do it will also be more durable. Ideally you need a vac pump to de gas the mix before pouring and it’s going to be a fair amount to try and mix by hand.
Don’t forget to wax and polish the hell out of whatever the buck is.

RustyNissan, is heat from the cure an issue in something that large?

I made a load of casts with embedded items a few years ago using silicone ice cube trays and polyester resin and there was a fair bit of heat in the mixing cup if I recall.

Im a bit out of touch with the casting side of things but I was involved in some fairly large cast projects (slurry impellers, diverter boxes etc) for the quarry/mining industries and heat/dimensional stability was never a problem. De gas/air bubbles were the biggest issue.

What is it you are casting/moulding?

Sorry for delayed replies.
Not sure I want the cost of getting a degasser too.

Making a dining table. With a resin ‘river’ cast between the two halves.

Presumably you’ve already seen this?

[video]http://youtu.be/wWkldrESy3Q[/video]

We do a bit of resin casting into wood now and again but mainly just filling holes from big knots etc, nothing that big yet.

The main issue I find is plugging the fissures and cracks. The resin seems to find its way out easily. We use blutac sometimes and tape too.
Presumably for your project you’re going to have to build some kind of tank to contain the pour.
Be a great project though.

Hadn’t seen that specific one, though something similar enough.

The idea of only being able to cast 3/8″ at a time isn’t ideal. Will see if I can find it for sale/what that costs though.

It’s just a diy project for a dining table. So tooling/resources are limited to what’s in the shed.

I don’t think the exotherm will be bad on that regardless of the material (assuming you don’t pick something not meant to be cast).

Some PUs get very hot but I’d assume that a casting specific formulation would take that into account.

I’d just our the whole lot in (although it would be a lot!) If you do need to mix up in batches you’d be fine pouring in one after the other when still wet.

Do you want it to be clear (even though it isn’t colourless?).

My familiarity is with epoxies. With a clear resin you shouldn’t need to degass. Any half decent formulator would be able to come up with a de-aerator and defoamer package so you didn’t need to.

I’d go with whatever you can get in quantity. You can get hard or soft materials with any of those chemistries. Polyesters and PUs tend to contain more nasty chemistry (Styrene and Isocyanates respectively). Epoxy isn’t great, particularly the amine curing agents used either!

As per Jonba above and the fact your in a shed – PU isn’t the ideal material for this purpose.

Good luck though -interesting project.