Adhesives. PVA Glues: White or Yellow?

[Doctor Chinnery]

It's been a long time since I put together one of Chris Foss's build-it-yourself kits. (One of the early single aileron servo Wot4s.) Anyway - in the building notes Chris strongly advises - insists even, that unless otherwise directed, White PVA should be used, specifically advising against Yellow PVA, or PVA that becomes yellow as it dries/cures. I used Resin W when I built my first Wottie, I see that it's still available and not too pricey. As I recall the only draw back was the length of time that Resin W took to dry. What do other members of the congregation use, that might speed things up a bit, i.e. faster grab/dry/cure times giving at least as strong a joint and with the caveat that it comes out of the bottle white and dries either clear or white?

Edited By Doctor Chinnery on 15/12/2020 01:07:25

[Ron Gray]

Gorilla Glue white, dries clear, fairly quick grab and dry time and very strong.

[DaveyP]

If it's a balsa/ply kit I would use Titebond wood glue, not the fastest to dry but very strong and sands well.

[Nigel R]

cyano pretty much everywhere, very thin / hot for most stuff and thick for birch ply / ply.

PVA for wing bandages (instead of epoxy or poly resin) and bead foam / wood joins - I avoid the cheapest stuff but I don't deliberately buy expensive fancy PVA

slow set epoxy for firewalls and UC mounts

contact adhesive for ply doublers and wing sheeting

canopy glue for canopies and hinges

that covers most things I think

[Chris Channon]

Stick ? with resin W. Never had a joint fail using it.

Regards

Chris.C.

[John Muir]

So long as it's a quality brand they're all much of a muchness. Yellow glues are just PVA with an added 'aliphatic modifier' which changes the properties of the glue according to the manufacturer's requirements. Usually it is to make the stuff easier to sand as ordinary PVA is a bit rubbery, but the trade off is it might be a bit more brittle. In practice any decent PVA will produce a joint that's stronger than the wood it's joining so it doesn't really matter. The yellow colour comes from a dye added to make the glue look different. Some white glues contain aliphatic modifiers but just don't mention it on the label. There's even some that are tinted brown.

This is all gleaned from much searching about on the internet so don't ask me what an 'aliphatic modifier' is!

[Phil McCavity]

I read it that you want to follow the Chris Foss recommendation so White Gorilla is a good choice, it's as good as Titebond and Resin W for balsa with the benefit of being sandable.

[kc]

I always use Resin W ( now labelled Evostik Wood Glue - as well as Resin W in small print) available locally but check prices as they vary greatly.

Supermarkets sell stuff in green bottles but it is nothing like Resin W! Try a sample of any glue you intend to use and test to destruction - if the wood fibres dont fail before the glue fails then it's not as good as Resin W

The first thing I ever glued with Resin W is a cabinet with drawers from 9mm birch ply.   Made it about 1966 and 54 years later the joints are still as good as new and still using it in my hobby room.   ( 6 years in an unheated shed and 48 in a centrally heated house )

Edited By kc on 15/12/2020 13:12:05

[Tosh McCaber]

I've used Titebind Ultimate for many years (in appropriate areas), rather than PVA, which dries rubbery, and is difficult to sand. Don't know why Chris would go with PVA over aliphatic? does anyone know (maybe best to ask the man himself!)

Edited By Tosh McCaber on 15/12/2020 13:30:16

[Brian Sweeting 1]

Some people recommend certain glues because of allergy concerns.

[Andy Stephenson]

I find that a butt joint made with white PVA can go somewhat flexible in hot sunshine, it doesn't sand well either. I think Foss' recommendation comes from some rather old fashioned thinking. Having built entire models with cyno and being warned that it makes the airframe too rigid and vulnerable to cracking under stress but having no such problem, I conclude that any glue will pretty much do the job. I do, though tend to use aliphatic these days but this tends not to sand too well either. Back to good old fashioned balsa cement I guess.

As far as Gorilla glue is concerned there are quite a number of different types marketed under the name Gorilla so it really needs clarification which one is being referred to.

A.

[John Lee]

Posted by Tosh McCaber on 15/12/2020 13:29:04:

I've used Titebind Ultimate for many years (in appropriate areas), rather than PVA, which dries rubbery, and is difficult to sand. Don't know why Chris would go with PVA over aliphatic? does anyone know (maybe best to ask the man himself!)

Edited By Tosh McCaber on 15/12/2020 13:30:16

The instructions appear to be unchanged since when they were written, which is 25+ years ago for the Wot4 Mk3. I've the greatest respect for Chris Foss but things have moved on with glue formulations over that time.

+1 for Titebond for me.

[Matt Carlton]

Evostik Wood Glue for most joints and never had a failure. The only caveat is that it is quite damp so be sure to weigh down things like doublers as it can curl up. If the longer grab time bothers you, I sometimes run a bead with gaps and use CA in the gaps to get an instant hold while the woodglue dries if it's a hard to clamp joint.

Doesn't sand well, so wipe off with a finger in a damp cloth. Makes a really good filler with balsa dust.

CA for everything else apart from firewalls, wing joints etc where I use epoxy.

Stabilit Express used to be my go to for sticking formers in fig/abs fuselages but not seen it for ages.

[Nigel R]

"Having built entire models with cyno and being warned that it makes the airframe too rigid and vulnerable to cracking under stress but having no such problem,"

Sums up my experience with cyano - been using it for donkeys, the wood breaks long before the glue.

Those thin applicator tips make the experience of using it much nicer - you can get just the right amount (i.e. very little) on a given joint.

Or, as I use, 1.5mm PTFE tube - available on ebay and costs pennies by comparison to the branded applicators. Cut about 2" at a time, and toss it if it blocks up.

CA is also excellent for sticking your fingers together, permanently attaching items of clothing to your skin, and is particularly good at joining wood and flesh.

[Robin Etherton]

In a past life I used to work for Tate and Lyle and carried out many trials on glues including pva’s. We had about 50+ different formulations of pva in use on the packing machines. Before working on these I had always thought pva was pva was pva, not so.

Personally I only use ca these days from the pound shop(4 20g tubs for a quid). Yes it is a little brittle but good old balsa cement is always there for backup. Cant beat ca for a quick build.

[Phil McCavity]

Posted by Andy Stephenson on 15/12/2020 14:00:42:

As far as Gorilla glue is concerned there are quite a number of different types marketed under the name Gorilla so it really needs clarification which one is being referred to.

A.

There's only one white wood glue under the Gorilla brand but the brown poly glue is also useful in modeling.

Edited By Phil McCavity on 15/12/2020 16:14:34

[Tim Flyer]

One advantage with PVA and to some degree aliphatic is that a heat gun can allow emergency disassembly if you make a mistake. Cyano is harder to release and gives reduced working time. Both pva and aliphatic stick well to heat activated covering film .

Edited By Tim Flyer on 15/12/2020 17:27:34

Edited By Tim Flyer on 15/12/2020 17:55:59

[Allan Bennett]

I use cyano a lot, but I also like Wickes own brand 'Weatherproof Wood Adhesive - Interior & Exterior'. I can't find the word 'PVA' on the bottle, but it looks and feels like PVA, and it grabs very quickly and sands quite well. Much cheaper per ml than small bottles of modelling PVA, and was recommended to me by my local model shop!

[Martin McIntosh]

Forget old fashioned PVA, use Titebond aliphatic for those bits where thin ca is not suitable. I even use ca for firewalls because it soaks right into the wood whereas epoxy will not. The drawback with water based glues is when laminating. As stated above, you can cheat by dabbing a little ca here and there. Another solution is to wet the opposite sides with water which will even out any warping while the wood is clamped and the glue drying.

[Mastercrashman]

Chris Foss does suggest that construction with PVA gives joints more flexibility.

I use Deluxe Speedbond PVA. It contains a solvent for faster drying.

It would appear many PVA glues contain fillers. The Speedbond doesn’t have any fillers and appears slightly thinner/runnier which I prefer.

[bjk896]

I have read so many glue Posts across the waves, I'm a bit confused. I will be starting a new build with Depron. (Its a 48" Herc). I know UHU Por is the recomended glue for Depron but the oneshot placement of components is limiting to an old fella like me.

So-o-o-o there seems to be a reluctance of posts to outright recomend or deny PVA, so please -

PVA with limitations or

PVA only with aliphatic or

PVA any old white stuff pupporting to be Polyvinyl acetate or

dont touch it with a 40 foot pole ???

[Denis Watkins]

UHU por can be used in the 1st few minutes wet/wet

Yes, it is incredibly strong when left 10 minutes then mated up in one shot fashion

But, as always, if you dry fit 100% certain of being all square 1st, make sure everything fits

Then wet both surfaces with the UHU por, and join accurate as possible; you do get some wiggle time.I

Otherwise I do use resins for strength

Resin W white

Titebond yellow

Aliphatic Resin yellow

Am not a fan of PVA