Specific issue sanding clear cast resin

[poorusher]

Hello

This is my first post, so hopefully I won't get my head bitten off (I did trawl the forums to see if this problem had been reported).

I have just started out embedding objects in resin. All my stuff so far has been rectangular or cubic, I use metal cake tins. Very happy with the moulds.

Each side is waxed before any resin is poured. The issue I am having is that the five sides that were waxed seem to sand fine, but the exposed surface layer appears to be clogging up my sander (using a random orbit sander).

Is there a way of preparing this surface before sanding? I do have an angle grinder for rougher treatment but would rather avoid using that if possible.

Hopefully someone on here can give me some pearls of wisdom.


Thanks
Luke

[mangozac]

Hi Luke, welcome to RA!

We try to refrain from biting off heads around here - I personally find them a bit bony

Interesting problem you're having. Is the upper surface a very obviously different finish compared to the others prior to sanding? I would expect it to have a few bubbles and the like on it. It's not particularly gooey (as if there's an uncured layer or something) is it?

What grit count have you gone down to with the orbital sander?

[poorusher]

Hola

Thank you for the reply.

I've actually spoken to some friends who make resin kitchen units. Their recommendations:

Post cure: put the resin in an oven at low temperature to harden.
Pre-cure: Apply talculm powder to surface layer.
Pre-cure: Apply wax in styrene to final poured layer.

The latter two methods stop air coming into contact with the top layer.

I have yet to test them.

Someone also recommended wet sanding.

For info, when I have sanded a piece and this has not been an issue, I use:

40, 120, 240, 400 and 600 grits.

The clogging was happening with the 40 grit.

The issue I face is how to sort the existing post-cured resin pieces. I can apply the other fixes next time I come to pour.

Hopefully this will work in the future, and this post will be of use to someone

[Fleafa]

If you are using polyester clear resin then this is a common problem. The addition of wax in styrene solution should solve it. Failing that, you could pour some rubber as a flat sheet, maybe reinforced with plasticard/hardboard, and place that on top of the open part of the mould once the polyester is poured.

[mangozac]

[Fleafa]

Clear casting resin has been engineered so that each time the resin cures it leaves a tacky surface for the next layer to be applied.
Preventing air coming in to contact with it as it cures will stop this.

[mangozac]

Aha that makes sense!

[Munkey Joe]

I never knew that either.... I learn something new EVERY DAY...... Awesome!

[poorusher]

Yes I am using Clear Casting Polyester Resin, thank you for this, it's good to have it confirmed.



Luke