Need help fiberglass staying tacky

[DCockey]

Product page for the resin shown in photo in original post: Boatyard Polyester Resin 1 GL; Non-spec resin. MEKP sold separately. - 128745 https://www.fgci.com/item/128745/Boatyard-Polyester-Resin-1-GL-Non-spec-resin-MEKP-sold-separately-/ From the page (bold added):

Boatyard Polyester Resin 1 GL; Non-spec resin. Contains a mix of different types of resins: ortho-, iso- & low profile. May or may not contain wax.

Boatyard Polyester Resin is a non-specified resin that contains different types of polyester resins and wax. Material may cure hard and tack-free due to wax. If so, product will need to be sanded prior to adding another layer in order to promote good bonding.

Step 6: Add sanding aid (Product #123833) to the final coat to allow a full cure and a tack-free surface. Refer to Sanding Aid Chart for quantities.​

Looks like the resin could be anything which qualifies as "polyester resin".

Some polyester resins without wax do not cure on the surface due to the presence of air. Product 123833 contains wax which allows the surface of air inhibited polysester resin to fully cure. Sanding Aid 1 Qt. Seals the surface & allows air to cure at the surface. - 123833 https://www.fgci.com/item/123833/Sanding-Aid-1-Qt-Seals-the-surface-allows-air-to-cure-at-the-surface-/

Interesting that no one picked up on Gonzo's post:

Is the resin waxed? Otherwise it will stay tacky.

 

[Mr Efficiency]

DCockey, I said as much early on...…" If it is unwaxed resin, which I assume it may be, it will stay tacky to touch. "

 

[BlueBell]

I picked up on Gonzos comment but it doesn't get us anywhere because we don't know if it's waxed or not.

Here's a quote from the same spec sheet:
"This is an economical laminating resin for repairs on boats, small parts production, autos, etc. Not recommended for use below the waterline."
That's a bit of a show stopper for me.

 

[ondarvr]

Unwaxed resin will still cure tack free, it just takes longer.

Having far too little catalyst is a more likely cause.

 

[Mr Efficiency]

It will cure tack free eventually, when humidity is low enough. But the laminate will have stiffened up long before that. As you say too little catalyst, something wrong with his calculations there I think. 8 drops is nothing.

 

[Mr Efficiency]

maybe it was supposed to be 8 drops per oz.

 

[Reefdog]

Thank you all, It took over 24 hours but it finally cured. I took the advice of moving the transom into a hot shed. That seemed to make the difference. It has a strong bond of both layers of 1708 and it tack free. I bought a new bottle of the catalyst for the other side. I will let you know if there is a faster result

 

[rxcomposite]

There are two types of resin being sold. Promoted and unpromoted. Promoted means it has cobalt in it and has a short shelf life. Unpromoted means no cobalt and will keep long but you have to add cobalt before adding mekp. If unpromoted, it will likely not cure no matter the amount of mekp. Cobalt is an initiator and preps the resin for catalyzation when mekp is added.

There is also the waxed and unwaxed variety. The waxed one, you use as a final layer where the surface is exposed to air. The wax floats to the surface shielding it from air and it cures. The unwaxed one will not cure in the surface and will remain tacky. However, if sandwiched between two boards, air is inhibited and it will cure. Unwaxed is also used when you are laminating in several layers. The last one, being exposed needs wax additive.

 

[ondarvr]

The retail market doesn’t sell unprompted resin here.

Under catalyzed resin may get hard, but that doesn’t mean it cross linked correctly, which results in poor physical properties.

 

[BlueBell]

Agreed.
MEKP is a 1% - 2% ratio to resin.
Anything more or less screws with the copolymerisation reaction
And in this case, his 10 drops/8oz is 0.15%

 

[Juliamarie Palero]

3 answers
1Not enough mekp.
2 your lay up temp is too cold.
3 how old is the resin?