Avoiding glue ridges.

[Munty Scruntfundle]

Hi there.

I've been gluing odd blocks of scrap together for turning, so far so good. However after sealer and sanding and sealer and sanding and waxing, I'm getting very slight ridges where the glue lines are.

After sanding everything feels lovely, but after any wet/goo finish the ridges appear. Only tiny but you can feel them.

Is there any way to minimise this?

Many thanks.

 

[CHJ]

What glue are you using?

 

[Munty Scruntfundle]

Erm, I think it's a Bostic or, Evo-stik. It'll be general purpose stuff I've used for more structural purposes.

 

[CHJ]

Probably a PVA then.
PVA glues can creep, not significant on cabinet making or general wood projects but can lead to joint lines moving enough to be felt as the wood adjusts to moisture or dries out over time in close segment work.
Surprised though if that is happening so quickly as you are finishing.
Not sure about your 'sealing' comments refering to wetting, what are you using as a sanding sealer.

 

[Dalboy]

One important thing is that all woods are dry, also some woods move more than others and as CHJ stated Pva can creep as well.

 

[sunnybob]

how long are you leaving it clamped tight? I mean TIGHT!.
You shouldnt get any pva glue moving afterwards unless you didnt put enough pressure on to start with.

 

[Munty Scruntfundle]

I'm clamping the bits as tight as I can possibly turn the handles. I could probably find clamps that had a better handle design though. So far the bits have been left for 48 hours or more.

It's maybe worth mentioning this is old dry bits of chopped up pallet, I have no idea what this wood carried, what leaked, where it travelled etc.

If not PVA, which this is, what should I be using? Or what might avoid the issue?

Thanks for the feedback so far, this is all valuable stuff.

 

[Doug B]

The best glue for segmented work is Cascamite, as Chas has said you can get creep with PVA I made this mistake years ago on my first piece of segmented work, it didn’t take long to be able to feel the joints & definitely not something you want after spending a lot of time assembling a blank.

 

[CHJ]

….
If not PVA, which this is, what should I be using? Or what might avoid the issue?
...

Cascamite; It will not give in the joint once cured, it dries brittle hard, although it has a reasonable open time you would have difficulty in separating closed joints after only a few minutes if not seconds at normal room temperatures.

This does have its consequences for closed segment work:-
1. You must ensure that the wood you are using is stable and at a moisture level relevant to its final placement location.
2. Be very aware of the relevant grain direction of mating pieces and whether they will result in excessive opposing grain direction distortion if humidity level changes, and endeavour to mitigate this movement by supporting or confining it with other plies, rings etc.
3. Any failures resulting from getting 2. wrong will lead to either an end grain joint letting go or a longitudinal split through a segment if the side grain joint is stronger than the wood.

Regarding the wood, I'm afraid that Pallet Wood is unlikely to provide you with a very satisfying results unless you are very selective and are prepared to establish a controlled drying regime, I would suggest that using relatively expensive Cascamite with it would be an unnecessary waste.
By all means develop your handling methods and techniques using whatever wood you have to hand but using anything but quality seasoned stock, albeit offcuts, is likely to lead to frustration.


On clamping of the joints, ring the joints together if possible to even out the glue line and expel excess and clamp firmly, no need for knuckle bruising pressure.

 

[Munty Scruntfundle]

Being impatient and not checking back here before searching around, I picked up a small bottle of Titebond II and III. It's a lot better. Number 2 behaves just like pva, and probably is, 3 is a bit thinner, flows really well and joints feel extremely smooth. I'll keep an eye on the test pieces and see how the finish moves over the next couple of months. (If it does at all)

I'll be picking up some clementines today.

Thanks for the advice. )

 

[Munty Scruntfundle]

Auto correct!!

 

[sunnybob]

I use titebond 111 quite a lot. Once set I have never had it move, but it does take up to a quarter hour to set hard enough to move the piece around.
It also dries brown, so dont use 111 on light coloured wood unless you want all the joints to show.

 

[Phil Pascoe]

how long are you leaving it clamped tight? I mean TIGHT!.
You shouldnt get any pva glue moving afterwards unless you didnt put enough pressure on to start with.

PVA is well known for creep regardless how you've used it.

 

[sunnybob]

I obviously am using mine wrong :roll: :lol: :lol:

 

[selectortone]

If Titebond 'creeps' why have just about all guitar builders large and small moved over from hot hide glue to Titebond? If you're making a guitar the last thing you'd want is your joints moving.

I have an acoustic guitar I built at the Totnes School Of Guitarmaking in 2006 and ALL the joints (and there are lots) are in exactly the same place as they were when I brought it home. I have made a few others and have never had a customer complaint in this regard.

 

[Lazurus]

Another cause for ridges is sanding, if the wood is softer than the glue line it can sand away leaving the glue proud.

 

[CHJ]

If Titebond 'creeps' why have just about all guitar builders large and small moved over from hot hide glue to Titebond? If you're making a guitar the last thing you'd want is your joints moving.

When we are talking about Creep in relation to Close Fitting Segments we are talking about 0.005-0.001 " movement (0.01-0.03mm say) which I can assure you can be felt across joints in polished pieces especially if it's a join between long and cross grain pieces that have moved due to moisture changes.

I doubt such movement is noticed or felt in the majority of applications.

 

[CHJ]

how long are you leaving it clamped tight? I mean TIGHT!.
You shouldnt get any pva glue moving afterwards unless you didnt put enough pressure on to start with.

PVA is well known for creep regardless how you've used it.

Some brands are specifically marketed as "Low Creep" but they can still flex causing some movement, which for the majority of cabinet work is probably a good thing.

An interesting discussion on the subject here in relation to Musical instruments.

 

[selectortone]

If Titebond 'creeps' why have just about all guitar builders large and small moved over from hot hide glue to Titebond? If you're making a guitar the last thing you'd want is your joints moving.

When we are talking about Creep in relation to Close Fitting Segments we are talking about 0.005-0.001 " movement (0.01-0.03mm say) which I can assure you can be felt across joints in polished pieces especially if it's a join between long and cross grain pieces that have moved due to moisture changes.

I doubt such movement is noticed or felt in the majority of applications.

Hmmmm. Still not convinced.

I turned a vase out of plywood recently for a contest at our turning club. It was glued up with Titebond original and comprises 32 separate pieces of 18mm and 12mm ply and involved a number of sub-assembly glue-up operations before the main glue-up and assembly. It is fully hollow.

I can't feel any ridges or whatever after six weeks. (Neither could the judges, it won 1st prize. Not wishing to blow my own trumpet, but I was complimented on the jointing)

My guitar is right here by my left elbow. I can't feel any creep ridges on that either and it's 12 years old.

 

[Setch]

Lots of guitar makers still opt to make critical stressed joints like the bridge to soundboard, or headstock scarf using hide glue, or fish glue, precisely because titebond creeps.

The only reason for using titebond or other aliphatics over hide glue (in luthiery) is convenience.