Hi, I have used EL2 resin with slow hardener to coat the inside of a moulding with the intention of sanding and polishing it to give it a nice finish on both sides, its been 4 days now and the surface is still not hard enough to sand.

When I have done this before with the fast hardener it is good to sand after 24 hours or so,

Is it just a matter of leaving it for longer, or have I messed up somehow?.

Any Ideas,




Drew.

Hi Drew,

What temperature are you working at and has it been humid where you are? EL2 with the slow hardener can take up to 30hours at 20C to cure so if your work temperature is cooler then the cure time would be longer.  If below 15C the cure time might be significantly extended and also the long cure time could leave the resin vulnerable to damage from moisture absorption, especially if the working environment is humid or damp.

It could also be a mixing error, either in the mixing ratio or mixing technique.

Getting the part in to a warm place 20C or over for a good few hours might help it finish the cure if there is nothing seriously wrong with the mixture.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Hi Warren,

Thanks for your quick reply,

Temperature wise, Probably 15-18 deg to start with, now I have the heating cranked up to 20-25 during the day but I have to turn it off at night (don't want to burn my shed down).

Mixing wise I'm pretty sure I got it right, the left overs in the pot has gone off like a rock.

Its Strange, it has "gone off" but its still greasy and a bit tacky on the surfice if I try and do anything to it.

I guess I will have to give it some more time and see how it goes.




I will let you know how it goes,




Drew.

If it is hard but just a little greasy/tacky then that might have been due to low temperature or a very slight mixing/measuring error.  You should be able to clean the greasyness off or worst case give the surface a very light sand to remove it.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

I am having similar probs with fast hardener. I would expect it to set fairly fast. It has not been. I mixed a little more hardener into the leftovers and that seems to have cured. I am using small quantities. Can I edge up the amount of hardener to make sure?

No, you should not increase the amount of hardener as that will imbalance the mix ratio.  As you are using small quantities you may well be introducing errors into the mix causing the problems.  With small batch sizes, it can be hard to remain within 1% mixing accuracy unless using jewelry scales or similar.  You then get factors such as uncured resin in the corner of the mixing cup and up the sides can now be "significant" enough to upset the mixing balance and cause errors.  In such cases it is often better to have a bigger batch size and accept some waste knowing the rest will cure properly rather than risk the resin not curing properly with a much smaller batch.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

I think I will try wetting the hardener cup before I weigh out. Should retain the same amount. Would weigh in 1, but it starts to gel too fast.

Working OK now. Was too cold as well. Amazing what a fan heater can do. Also keeping the chemicals warm beforehand.

Hi Warren,




After a week most of it went off, only a small area remained soft which was finally removed with a scraper and elbow grease.

I gave it another coat using fast hardener and it all went ok.

must have been something I did.




I have another project coming up which is sealing a concrete worktop, my plan is to give it a sealing coat with elp2 and the give it a coat of Glass cast to finish it off, what do you think?




Drew.

Hi Drew,

You can seal the surface with GlassCast rather than need 2 separate resin systems.  The GlassCast has better UV resistance than the EL2 overall.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant