hi there all
The small tins of resin which you purchase from the Auto shops, such as David's resins, there are 2 things which we must consider and be aware of, when using them.
The environment you are going to use it - either in/outside - and also how long the tin has been stood on the shop shelf.
First of all, all of the resins we use in our hobby are called Pre-accellerated resins - meaning there is an accellerator blended into the resin on manufacture. This is the actual agent which hardens the resin. The haradener or catalist is the 2nd part to this match. When the resin has been standing for a certain length of time, the mixes in the resin start to settle to the bottom of the tin. So, when we come to using them, if we have not shaken the resin up for at least a good 20 mins I MEAN A GOOD 20 MINUTES the chances are you are not using the correct mixture of resin. Sometimes, you will find, as you work down the tin without shaking it; the resin mix that we have either goes off extremely quickly or doesnt go off at all.
The 2nd thing to consider is when we are using Davids resins they are produced for the DIY market where the person who is more likely to be working in a cold garage/outside environment. So, to aid curing or the resin hardening, they advise a larger/maximum amount of hardener mix. Now, if we are working in an environment which is indoors at a temperature of between 20-26 degrees C - we must begin to start to reduce the hardener mix.
Sometimes, when we mix too much hardener in, this can also create a situation where the resin stays tacky for a long time - as well as having the other way - where we havent mixed enough hardener in.
Under normal working conditions and correct hardener/resin mix; you should get at least 20 minutes working time out of the resin - regardless of the amount you mix. Obviously the larger/shallower tray/dish you mix your resin in - a slightly longer working time you will have.
Hope this is of some help.
aye
john e
bluebird