PVA - does it dry clear??? Mine doesn't?

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dan8400
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PVA - does it dry clear??? Mine doesn't?

Postby dan8400 » Thu Dec 16, 2010 11:11 am

Hi,

I am using a large tub of PVA i bought. Did a bit of glue-ing a couple of nights ago and it's still white. Will it eventualy dry clear? Or is it the wrong sort of PVA (if there is such a thing)

Thanks
Dan
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raistlin295
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Re: PVA - does it dry clear??? Mine doesn't?

Postby raistlin295 » Thu Dec 16, 2010 11:31 am

Dan,

As far as I'm aware, cheaper PVA adhesive is bulked out with chalk which means it doesn't dry colourless, instead looking a milky white.

I use the Admix PVA available at Wickes. It dries clear and is reasonably cheap in 5L bottles.
Paul

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slackbladder
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Re: PVA - does it dry clear??? Mine doesn't?

Postby slackbladder » Thu Dec 16, 2010 12:15 pm

Also consider temperature. In a cold environment PVA will take longer to cure and hence to clear. (I am not inferring that is your problem its just a note from an old carpenter who has used gallons of the stuff)
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dan8400
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Re: PVA - does it dry clear??? Mine doesn't?

Postby dan8400 » Thu Dec 16, 2010 1:17 pm

Thanks slackbladder, I was hoping that was the case. Need to sort proper heating in the railway room.

I will keep in mind about cheap PVA so thanks to you raistlin295 as well


Thanks
Dan
My Layout Thread: viewtopic.php?f=22&t=30117

the flying irishman
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Re: PVA - does it dry clear??? Mine doesn't?

Postby the flying irishman » Sun Dec 19, 2010 2:53 pm

So, if I bought some good quality pva, and poured some into a specially designed water-course set aside on my baseboard... would it dry clear to make a stream? :?: :idea:

cheers, lewis.
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slackbladder
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Re: PVA - does it dry clear??? Mine doesn't?

Postby slackbladder » Sun Dec 19, 2010 9:42 pm

I have read that some modelers do use pva to create water, however I think most use clear varnish. The best answer I can give you is why not simply try pva on a small test area?
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dieselbob
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Re: PVA - does it dry clear??? Mine doesn't?

Postby dieselbob » Mon Dec 20, 2010 12:18 am

Hi Dan
I used Resin W woodwork adhesive to create a small pond on my layout, because I read somewhere that it dries clear.
Unfortunately after a couple of months it was still milky, I did put it on thick in an attempt to get some depth. I painted it over this morning and will go back to my old method of a few coats clear varnish.
Cheers
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Re: PVA - does it dry clear??? Mine doesn't?

Postby m8internet » Mon Dec 20, 2010 5:23 am

As always, test on a small area to see how much is required
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Bufferstop
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Re: PVA - does it dry clear??? Mine doesn't?

Postby Bufferstop » Mon Dec 20, 2010 10:16 am

For streams and shallow puddles I've always used polyurethane varnish. Dries with a shiny surface but just a bit darker when you peer into it. I think PVA dries to almost clear, a thin layer seems OK to me for a window but the greater the depth the cloudier it seems to get. Mind you, last year I bought some for the first time in fifteen years after finishing the stock I found when told at work "if you throw out everything in that room, you can use for a workshop." It came in 5litre bottles, unbranded but labelled "School Glue"
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the flying irishman
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Re: PVA - does it dry clear??? Mine doesn't?

Postby the flying irishman » Mon Dec 20, 2010 5:10 pm

Ok, cheers, ill probably use the varnish then! When making water features, has anyone applied layers of varnish or all in one go?
Cheers, lewis.
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raistlin295
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Re: PVA - does it dry clear??? Mine doesn't?

Postby raistlin295 » Mon Dec 20, 2010 6:15 pm

the flying irishman wrote:Ok, cheers, ill probably use the varnish then! When making water features, has anyone applied layers of varnish or all in one go?
Cheers, lewis.


Yes. It goes horribly wrinkly :(
Paul

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0121modeller
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Re: PVA - does it dry clear??? Mine doesn't?

Postby 0121modeller » Mon Dec 20, 2010 7:12 pm

Have you considered using quick drying clear varnish ?
A normal coating will be dry in 15 minuits, so re-coating layers is quicker than polyurathane, Although I used polyurethane varnish on my canal, 1coat took a day to dry (cold weather slows drying also).

Whatever you choose to use, then dont apply it too thickly, & as already advised; test on a small area first, as, if you apply cetain types of paint/varnish on top of another type of paint/varnish you may encounter a reaction between different types, (blistering, crazing, etc).

Keep in mind also that the first coating of "quick drying" varnish/paints will always 'raise the grain' of bare pine/softwood & It will bow & twist large area's of bare plywood under 9mm thick , a very gentle fine sandpapering between coats will cure raised grain on pine.

As for bare plywood, varnish/paint both sides of plywood if possible ASAP as to counter-act the bending. (Quickdrying is 'water-based' & its the depth limit of water penetration that makes the wood fibres swell causing plywood to curl & bend).
But if using polyurethane varnish, then these above effects will not be so extreme.

Dave.
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raistlin295
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Re: PVA - does it dry clear??? Mine doesn't?

Postby raistlin295 » Mon Dec 20, 2010 8:44 pm

When I was a kid I had a plastic resin moulding kit that was used to make keyrings, paperweights etc.

That resin could be poured quite deep and as a result you could encapsulate small items and there was never a wrinkle to be seen.

I wonder if such material is still available and whether it would make realistic water-based scenic effects?
Paul

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0121modeller
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Re: PVA - does it dry clear??? Mine doesn't?

Postby 0121modeller » Mon Dec 20, 2010 10:06 pm

Raistlin, that description sounds like a product generally known as Clear casting resin , I created an inch depth with a single application when I used this product for my 1st canal modelling project that I made in 1994.
Clear casting resin was a rare product to obtain back then, & I'm not sure about the availability of this now, due to possible reasons I've said below.
It consisted of a 2 part compound in a metal container ( 1part to 6part mixing I think was required ).

I'm not sure, but I think the health & safety issues were regarded as too risky for the average or inexperienced, or incompetant modeller, as I think if mixing was'nt done properly, the heat generated during the curing process would lead to possible combustion/fire risk caused by the uneven mix curing in a poorly ventilated room or confined area.

I remember it gave the room a highly, maybe slightly toxic fumes/smell, a rather similar smell to that of liquid poly or similar 'plastic weld' solvents.
The curing to set reasonalbly hard took 2 days.

There was (or still is) another product made by Woodland Scenics which consisted of a bag of yellowish/white /clear/opaque pea sized pellets which you'd heat up in an old saucepan to make a pourable liquid, I remember reading that it could be possible to re-use it if removed, broken up, & re-heated/melted.

De-luxe modelling materials make a product called E-Z water (or something like that) also.

Dave.
Scratchbuilding 4mm scale JXA scrapwagons ; - viewtopic.php?f=6&t=37620
Scratchbuilt & kit built grappler claw cranes ; - viewtopic.php?f=6&t=36342

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raistlin295
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Re: PVA - does it dry clear??? Mine doesn't?

Postby raistlin295 » Mon Dec 20, 2010 11:41 pm

Yes Dave,

Thinking back, I remember the characteristic smell and I also remember that if the mixing wasn't done properly, the heat could melt the plastic cup we sometimes used to do the mixing in.
Paul

Finsbury Road My Layout


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