PVA

[Laserbones]

How long should you leave PVA on to cure gelcoat, before wiping off with presumably acetone, or maybe white spirit? I@m going to finish with flowcoat, but I've got a lot of debris to sand off before final coatings. I'm working outside and of course the temperature is dropping, but the wind has blown seeds and muck which has stuck to the gelcoat

 

[Roberto]

Thought it was Positive Vorticity Advection

 

[iamtjc]

PVA is water soluble so it washes off in warm soapy water.
You mix alcohol with an aqueous solution simply to speed the drying time.
Gelcoat under PVA should harden in 24hrs - 48hrs if it is going to harden at all.
I have found PVA less reliable than sticking a sheet of pvc on top of the patch though obviously it is a better option on a non flat surface. Possibly I didn't always build up a thick enough layer of PVA. It needs a few coats.

 

[PaulRainbow]

How long should you leave PVA on to cure gelcoat, before wiping off with presumably acetone, or maybe white spirit? I@m going to finish with flowcoat, but I've got a lot of debris to sand off before final coatings. I'm working outside and of course the temperature is dropping, but the wind has blown seeds and muck which has stuck to the gelcoat

Don't use acetone on new Gelcoat.

 

[VicS]

How long should you leave PVA on to cure gelcoat, before wiping off with presumably acetone, or maybe white spirit? I@m going to finish with flowcoat, but I've got a lot of debris to sand off before final coatings. I'm working outside and of course the temperature is dropping, but the wind has blown seeds and muck which has stuck to the gelcoat

A little puzzled by your reference to PVA

PVA ( polyvinyl alcohol ) is used as a release agent when laying up fibre glass in a mould.

Flowcoat is gelcoat resin containing wax. It is used as the final coat of gel coat when finishing a fibreglass item not being made in a mould. Mix the flowcoat very thoroughly to evenly disperse the wax throughout before measuring the required quantity and mixing in the catalyst.
Apply the flowcoat at the recommended thickness to ensure sufficient wax is present

I imagine the wax could be removed with white spirit if necessary. I agree with the above advice not to use acetone on new gelcoat.
.

 

[The Q]

PVA is water soluble so it washes off in warm soapy water.
You mix alcohol with an aqueous solution simply to speed the drying time.
Gelcoat under PVA should harden in 24hrs - 48hrs if it is going to harden at all.
I have found PVA less reliable than sticking a sheet of pvc on top of the patch though obviously it is a better option on a non flat surface. Possibly I didn't always build up a thick enough layer of PVA. It needs a few coats.

Not all PVAs are the same.
There are 4 grades of PVA,
Grade 1 as used in schools, fully water soluble, even after drying. Often not marked with grade
Grade 2, wet it, wait for some time till it goes soft to remove. Often not marked with grade
Grade 3, waterproof providing not submerged. Sold as waterproof pva,.
Grade, 4 waterproof even if submerged. You have to deliberately choose to buy this one.
The higher the grade the more expensive they are.

I use grade 1/2 for modelling railways, grade 4, for building work, furniture repaires etc.

 

[VicS]

Not all PVAs are the same.
There are 4 grades of PVA,
Grade 1 as used in schools, fully water soluble, even after drying. Often not marked with grade
Grade 2, wet it, wait for some time till it goes soft to remove. Often not marked with grade
Grade 3, waterproof providing not submerged. Sold as waterproof pva,.
Grade, 4 waterproof even if submerged. You have to deliberately choose to buy this one.
The higher the grade the more expensive they are.

I use grade 1/2 for modelling railways, grade 4, for building work, furniture repaires etc.

I think you are referring to PVA wood and paper adhesives. In this context PVA is polyvinyl acetate

PVA used as a mould release agent is polyvinyl alcohol.
.