Quick question - is it mild/warm enough to get cracking with the epoxy in an unheated garage? 

Thank you for your thoughts.

Yes, if you allow long cure times or use a fast hardener

It'll cure fine, but take a while.

If you have electricity you'd be amazed at what 5w strip heater (Towel dryer type thing) and an old spinnaker can do for glueing. Coating i wouldn't attempt yet without heat as there is still a risk of damp and the resin going milky.

Chris. 

Interesting re the milky bit. I have had to stain some wood using Coldron wood dye and when I put epoxy SP106 on it went slightly milky would this be the cold weather or a reaction?

TIA

The literature for epoxy notes that in damp conditions it will cure with a milky surface (amide/amine formation If I remember correctly).
This should be washed (water) then sanded to remove the bloom.

That's one of the reasons for using a warm(ish) workshop - probably >55F, and making sure that it's warmed until the epoxy has cured (that time depends on the hardner and the temperature).

I suppose it's possible that the stain and the epoxy have reacted - if it's a water based stain, then I guess you could have the bloom on the underside of the epoxy...

Colin

If the dye is water based it could be that you didn't leave it long enough. 

The milky colour is caused by moisture. cold in itself doesn't cause an issue other than that the resin takes ages to cure but, of course, then you are far more likely to get condensation and there is more time for damp to get onto the job.

If you're coating and it's going to go below about 8 degrees you need a small amount of heat just to take the edge off.

Regarding the colron dye - it is an organic solvent and therefore needs plenty of time to evaporate.  I used a clear cuprinol wood preserver on one boat to prevent rot, left it for 2 weeks and yet could still smell it when I came back - and that was in warmer summer weather.  When solvent dries it leads to a lowering of temperature (Vapour pressures, Charles Law and Boyles Law come into play as far as I remember from my A level physics and chemistry ) so if the temperature is lowered it could allow some almost invisible local condensation to occur and that could cause your milkiness.  Add this to our recent weather and I would say this could be the problem.

Thanks. I think Coldron is a spirit based stain!

Isn't spirit organic?

Yes!

So it should be OK. I recon it must be the cold/damp then.

Thanks anyway for the advice.

For what it is worth, I have found Blue Gee epoxy to be far less sensitive to temperature related problems than certain others.

Spirit based is ethanol and hence an organic solvent (C2H5OH if memory serves) so solvent will take a long time to evaporate at low temperatures.  One cheap and safe way to provide some background heat is to use 1 or two inspection lamps with 60 or 100w bulbs.  If the boat is covered with a tarpaulin or similar with the lights left on under the cover, the air around the area being worked on is raised quite a bit.

Dont leave a string of bulbs on under a tarpaulin on the boat. Did it once and three of the bulbs burnt their way through the boat and ended on the floor. Thankfully the lot didn't burn down. The epoxy did cure!