I found this on another forum the other day and thought it may be of interest on here, I'm thinking of trying this as a spray tack alternative.
Invisible Epoxy Infusion Spray-Tack
1. Start with a clean, small plastic ‘spritser’ bottle (any openable plastic bottle with a pump-action mister spray, like for hair-care products).
2. Mix up 10g of infusion resin with 3g of infusion hardener and pour into the bottle.
3. Add 10g of metholated spirits to the bottle (it must be purple meths, no white spirit, acetone, alcohol or anything else).
4. Shake the bottle thoroughly.
5. Spray a thin film of the spray tack over the surface of the mould.
6. Allow the meths to evaporate and wait around an hour or two for the epoxy to start reacting when it will become particularly tacky.
7. Stick your reinforcement to the tacky mould surface.
When you do the infusion, you will find that the tiny amount of spray-tack on the surface will cross-link with the resin of the infusion epoxy and become completely invisible with not even a trace of anything on the surface of your parts!
Found at http://www.talkcomposites.com/FindPost12697.aspx
a further comment:
Don't use the actual mixing ratio of the resin and hardener, use a ratio that is way off. Instead of 100:30 in this example, use 100:3 or 100:5. It's important that there is excess epoxy resin, NOT hardener. Without going into the chemical details, this converts normal resin into a sticky, gooey mess that can be stored for a long time (I have some samples that are several years old and haven't solidified) Such mixtures will thicken considerably but remain soluble since they haven't crosslinked. The large excess of resin in this case means the mixture also stays reactive, ready to react with other hardener molecules. This mixture will not go bad; once all the amine hardener molecules have reacted with their epoxy counterparts the curing stops and the mixture remains in its gooey state.
Dissolve this goo into a solvent and use it as your spray tack. Use sparingly, then there is no need to adjust the infusion resin mixing ratio. Your homemade spray tack will simply dissolve and disappear into the infusion resin, leaving no visible trace of its presence.
All resins and hardeners are a little different, so even if I remembered the exact numbers I used in these experiments they might not work well for other resins. (I used regular laminating resins and a really slow hardener with a higher viscosity than infusion resins).
If anyone wants to try this out, take several small airtight screw cap glasses, put 10 grams of resin in each container, and then add 2, 4, 6 and 8% of hardener or whatever numbers you feel might work. Then leave the mixtures alone for at least a day, maybe longer. Since there is no exotherm the curing reaction will take much longer to complete. Check the samples for goo/tack factor by poking them with a stick. They should be nearly solid. Dissolve some in acetone and apply by spraying.
If for example the 6% works fine, more hardener can be added to the 2 and 4% experiments so they aren't wasted.
So it may need a little play around with ratios - I'm temped to go with the 100:5 trial and see what happens :)
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