How to glue

[88v8]

I've always glued by applying to a clean dust-free joint and cramping up pronto.
However, when looking for some fresh Cascophen (then called Extraphen and now called Polyproof - why?) I found this description of how to glue:

DIRECTIONS FOR USE

To obtain the very best results the moisture content should be in the 12-14% range.
Timber bought as kiln dried and stored under cover will present no problem.

Perhaps as important as the glue is the preparation the joining surfaces, especially for Oak and oily timbers, Teak, Iroko etc.
Timber direct from machining has a slightly glazed surface and the surface fibres are compressed by rollers etc, far from ideal and it is essential that the surfaces to be joined should be ridded of this unwanted smoothness.
Use a scouring plane (blade with fine points), hacksaw blade, or very coarse sandpaper. Plywood must be treated in the same manner.
The gluing area should be abraded as close to bonding time as practically possible.

Dust with a bristle brush, oily timbers should be degreased with methylated spirit.

As important as preparation, is working in the correct temperature and that means, within reason, as warm as possible, 20C is ideal. At higher temperatures the glue becomes much less viscous, easier to apply and penetrates the timber instead of laying on the surface, a better glue line results.

For the best results both surfaces of the joint should be glued. Use good quality brushes. Surfaces once glued should not be exposed to the air for any length of time.
Do not over cramp; it’s possible to starve a joint this way. A minimum of twenty minutes closed assembly time should be allowed before the application of pressure.
Just bring the surfaces firmly into contact.
This will enable the glue to penetrate the surface fibres of the timber and avoid excessive squeeze-out.

Who knew?

I have to glue a drip-bar onto my garage door.
It's certainly not 70F out there. Need to close the doors and heat up the space. Oh, no doors. Doomed.

Ivor

 

[Penners]

Cascophen is a cross-linked (ie: chemically cured) glue, so it's important that it can penetrate the glued surfaces thoroughly before it cures - hence the need for abrasion. At lower temperatures the chemical reaction can be retarded.

For the application you have in mind, you may find it easier to use polyurethane glue, which doesn't require any mixing and is eminently suitable for external work. It works best if you damp the glued surfaces before using it. Be sure to cramp the mating surfaces together during its setting time, because it tends to foam slightly. This is good for gap-filling, but if you don't cramp, or you use too much of the glue, it can foam out of the joint. If this happen, trim it with a blade and sandpaper after it's set.

Typical polyurethane glues:-

http://www.screwfix.com/p/gorilla-glue-115ml/54593?kpid=54593&cm_mmc=Google-_-Product%20Listing%20Ads-_-Sales%20Tracking-_-sales%20tracking%20url&cm_mmc=Google-_-Shopping%20-%20Sealants%20and%20Adhesives-_-Shopping%20-%20Sealants%20and%20Adhesives&gclid=Cj0KEQiA2b20BRDj4buduIG-y9EBEiQAhgMGFVw7-sbPSgoJTj71-0UkSICXj22YG0M8DWmkADzTaeUaAkha8P8HAQ

https://www.orbitalfasteners.co.uk/en/products/everbuild-polyurethane-30-minute-wood-adheshive-professional-glue-750grm?utm_medium=google_shopping&utm_source=google&utm_campaign=google_shopping&gclid=Cj0KEQiA2b20BRDj4buduIG-y9EBEiQAhgMGFfuCPY5eTWsKAoPLEOzl_y-vDGrZVRKlewgoO8vvv54aAupv8P8HAQ

You'll almost certainly find some brand or other at your local builders' merchants. Personally I'm a fan of Gorilla Glue.

Be sure to seal the spout of your polyurethane glue tub thoroughly after use, and expect no more than 6 - 12 months' shelf life. So don't buy a huge tub.

 

[88v8]

Thankyou.
Oddly enough I've been using Gorilla, on the recommendation of a joiner, but its ultimate strength seems less than I recall with Cascophen, and on bare wood its yellowing is unsightly.
However, this job will be painted with my first attempt at linseed.
For which the temperature is also rather low. Hehyo.

Ivor

 

[DJH]

Should this topic be made sticky?

 

[Penners]

Should this topic be made sticky?

Not a bad idea, Doug, provided you understand that after a year or so it will harden into a solid lump and become unusable.

 

[Toby Newell]

Please disregard this post, I lazily assumed the glue was PU, Penners informed me it isn't so my advice is useless, thanks for pointing that out Penners.

Ivor

I think your glue is a polyurethane moisture cured adhesive.

All polyurethanes currently cure by an isocyanate catalysed reaction, this can be single component via oxygen cross linking or moisture cure (where adequate water or oxygen need to be supplied hence kiln dried would be no good unless moistened before gluing) or two component where the isocyanate catalyst is mixed before application.

The polyurethane glues have excellent cured film water resistance and faster grab times but are harder to apply compared to PVA glues for example.

The problem is that PU glue is typically more viscous than PVA, does not whet the surface as well (more surface tension) and the curing reaction (in this case with water) releases gas so the glue film is likely cause micro bubbles which can push the glued surfaces apart. Seeing as the strength of glued joints are proportional (to some extent) to the surface area of the plane surfaces abrading the surface in this instance helps to increase the surface area whilst also creating spaces for the micro bubbles to form without pushing the joint apart.

The PU expandable foam in a can is essentially the same thing as is the foam in your fridge and freezer which is made by squirting PU resin and a catalyst together in a big machine into a hole in the fridge cabinet, as also is the case with cavity wall insulation foam.

At 20 celsius they are being careful, knowing that people push things as is naturally human. You should be alright down to around 10 celsius as long as you pre warm the glue (put whole container into a warm area for a day before use) your application appears to be low load bearing so you should be ok. Adding a few 16G brads from a nail gun would be handy in an application like this.

Below 10 celsius weird things start happening and whilst most catalysed reactions will still proceed albeit slowly, the strength of the cured film may be sub optimal. I think if you pre wet the surfaces (i.e. increase catalyst) and pre warm the glue and affix with a few pins all will be fine.

 

[Penners]

I think your glue is a polyurethane moisture cured adhesive.

Actually, Toby, Cascophen is a cross-linked resorcinol-formaldehyde resin. As I'm sure you know, this glue is considerably less tolerant of not-quite-perfectly mated glue joint surfaces than a PU glue. So for most non-professional uses, PU tends to be a more satisfactory choice.

 

[Toby Newell]

Hi Penners

Actually I did not know that, thank you for correcting me, my advice was for a PU moisture cure glue so is NULL and VOID for the formaldehyde, thank you for pointing out my lazy mistake as I did not bother to google the glue and have never used it.

 

[Penners]

Very lazy, Toby - after all, you have nothing else to do all day, do you?! :wink:

 

[DJH]

I always enjoy reading your posts Toby. They are very informative...

In an earlier life, Cascamite was the glue of choice especially for gluing my foundry patterns which were subjected to having damp sand rammed over them and temperature variations (cold at night and in a hot atmosphere when the furnace was on) and I don't recall any problems with them falling apart.

It was easy to mix and apply to one side but I suppose the clamp time was quite long although any residue could be wiped off with a damp cloth. On reflection there was a lot of waste sometimes with leftover mixes going hard in the pot after an hour or so...I wonder if anyone still uses it nowadays...

Doug

 

[Flyfisher]

I remember Cascamite being widely used for boat building because of its waterproof characteristics, though my experience was back in the 80s when I used it to build a wooden 'Canadian style' canoe that is still in use, albeit infrequently, these days.

Perhaps it has been superseded these days by new fangled chemical technology, although it seems to still be readily available: http://www.axminster.co.uk/cascamite-powdered-resin-wood-glue-ax21688

 

[Toby Newell]

Very lazy, Toby - after all, you have nothing else to do all day, do you?! :wink:

Correct again! Actually I don't at the moment as I am in-between jobs. Of course that's not strictly true, I do have plenty of stuff I could be getting on with.

Sunday was a total day off as on Saturday I commuted to Camerton Hall in Workington to see a job which was a 700 mile round trip. Hopefully I shall be restoring the flood damage as the end of the month and shall post pictures.

 

[Penners]

I remember Cascamite being widely used for boat building

Yes, me too, FF. My father used Cascamite in the late '50s to build a small sailing dinghy for me - an 8ft pram-conformation craft called a Gremlin. It was hopeless! The dagger-board was too small to stop it sailing sideways, and it would capsize in the lightest of breezes!

 

[Toby Newell]

I still use cascamite, very occasionally, on antiques but my Grandfather used it extensively, I remember his glue pot! Although that may have been his rabbit skin glue pot come to think of it.

Wonderful stuff and makes you feel warm inside that they still make it.