Polyurethane Sanding Question

[David G4EBT]

Originally Posted by PsychMan

The sanding sealer has now arrived thankfully, any tips on using this with the wood dye? Other than applying it afterwards? I imagine I might have the same
Problem with this dye if I’m not careful - or use a different product suppose..

A lot of wood dye, as with varnish is water based these days.

To get dye to penetrate deep into the wood you need spirit dye which has much lower surface tension than water.

For example:

https://www.liberon.co.uk/product/spirit-wood-dye/

But you need to test the shade you choose on a piece of scrap because when it's in, it's in to stay. Walnut for example, can end up looking more like ebony if applied to some timbers such as oak. And yes, if you wish to stain wood, you need to do that before applying sanding sealer.

Well done on your perseverance - as Winston Churchill put it:

'Success consists of going from failure to failure without loss of enthusiasm'.

He was clever!

[PsychMan]

I stuck a piece of veneer on some scrap wood, applied the dye and then applied the sanding sealer as a test. Unfortunately even a light sanding and the dye was lifting, so it looks like I need a spirit dye...

On the plus side I found the sealer filled the grain very well indeed and it felt much smoother after a light sand. With the right dye I could be on to a perfect combination.

I find failure is something that needs to be embraced, anything that requires any level of skill requires at least a bit of failure to get there. In my case a lot as I tend to jump into projects head first whether I have experience or not. I’ve learned a lot of things and have learned them “my way” as a result, with a lot of help from this forum of course !!

Adam

[emeritus]

Reassuring to know that the spirit dye is still available. I could only get the water-based stuff at my local shop the last time I needed some, and it is nowhere near as effective. Better stock up before they ban it.

[AC/HL]

It appears to be freely available. No mention of pending restrictions: https://www.liberon.co.uk/our-produc...woodwork/dyes/

[emeritus]

I was mindful of the ban on spirit-based wood preservative, which I only found out about by chance a few days before it came into force, and was lucky to find a shop that still had a few of the old cans in stock. There wasn't much publicity about that.

[PsychMan]

Still not having the best of luck. The tetrosyl arrived and isn't tetrosyl, they subbed in another brand of car lacquer - but probably wont matter.

Applied Liberon spirit dye, which claims "new ethanol based formula", still managed to go through it when sanding the sealer....Ill just finish this box as it is I think and try for better on the next piece.

Again, looking back over my methods, perhaps I wasn't as "liberal" with the Liberon as I should have been. It did say apply liberally, and I tried but I applied it with a cloth, and It did seem to take to the wood quite fast. The trouble with a cloth is it ends up absorbing half of the stuff you're applying. On the next go I will apply it thickly with a brush and leave to sit on the surface for a minute or so, perhaps that is the secret.

This is all proving a lot harder than I first thought!

[ajgriff]

Just a thought but I would only normally use sanding sealer prior to applying a wax finish. Might use grain filler, depending on the type of wood, if finishing with lacquer. In all cases every coat must be fully cured before very gentle rubbing down is attempted.

Alan

[PsychMan]

I had waited 24 hours after applying the spirit dye before applying the sealer. I mainly used the sealer to try and fill the grain, it does a reasonably good job of that. I did notice a bit of dye on the brush when applying the sealer, so perhaps it interacted with the dye.

I did buy some "thixotropic"(?) grain filler, but I found it difficult to work with, it dried VERY quickly, and the dye in it was darker than I wanted. It seems difficult to fill the grain on walnut veneer if you want to use another dye, the thinness of the veneer is also challenging.

Hopefully I'll find a combination Im happy with. Its a good thing I have lots of veneer left over from the main project (record changer plinth), so I can test so many different products and methods. Ive had all sorts of lashed up projects and PCBs hanging around the workshop, so it makes sense to make boxes for them. I also have lots of ply offcuts Ive squirrelled away from DIY projects

[PsychMan]

Having another look at this problem I think Ive missed one key stage. I should have sanded the veneer after application to get it as smooth as possible FIRST, before doing anything else to it. I think what I had hoped would be achieved by grain fill is just unrealistic with some of the dramatic structures in this veneer. My attempts to do so after the sealer have required me to sand far too deep, thus removing the stain. I don't know how I missed this.

Again, the perfectionist in me has once more sanded off the veneer and started again

So now I will apply the veneer, sand smoothly as best I can without going through the veneer, water based stain - simply because I prefer the colour, cellulose sealer as smoothly applied as I can, and barely sanding at all before starting to build up lacquer coats. Again, VERY light sanding until I have built up enough layers. I hope this finally will achieve what I want!

[David G4EBT]

The only veneering project of any sized that I've completed which - though not radio related might be relevant to your project is a lidded box that I made for my son in which he had particular boxed sets of DVDs he wished to store. I made it with furniture grade beech through and through plywood (not DIY store construction grade ply) and veneered it in rift cut oak veneer, which I applied with traditional hide glue.

He wanted it stained dark oak (which wouldn't have been my choice), so having lightly sanded the veneer to 320g, I applied a coat of dark oak spirit stain with a brush, then when it had dried, applied a coat of shellac sanding sealer, diluted 50/50 with thinners (meths). Another light sanding and three coats of clear gloss auto varnish. See pics below. (Inside the box, I only needed to stain and spray the lid as I lined the box with felt covered panels of MDF).

Pic 1: Box showing underside of lid.
Pic 2: Box with lid on.
Pic 3: Box stained and finished.
Pic 4: Felt covered panels.
Pic 5: Panels in place.

Hope that might help a bit.

[Red to black]

I rather might have thought your son (about my age group, 50's) would have preferred the lighter un-stained finish, as I know my missus would have preferred that (women really do rule the world in my life )

Outstanding work all the same as ever with you David.

[crackle]

If you want spirit based wood dye https://www.blackfriar.co.uk/product/wood-dye/

Mike

[Uncle Bulgaria]

I have had success with simply wood glue and pressure, followed by some 180+ sanding (not too much as I find sanding very dull) and linseed oil or Danish oil depending on what I had. A few coats of that and some curing time and I think the result on this oak over plywood was just what I was looking for. I cut the edges off each side with a scalpel to deal with the overlap after the glue dried and sanded the corners off somewhat.

I think you'll have more difficulty the finer the figuring of the veneer and the thickness of it. With an open grain like oak, I didn't want to fill it so the finish is not flat but slightly dimpled as the oil/varnish has not levelled out the grain completely.

[PsychMan]

Ive found applying the veneer itself very easy. Achieving exactly what I wanted, which was a darkened walnut veneer with filled grain and a flat gloss finish, not so much.

Through experiments and advice from David mainly, Ive found in general this is the approach ill be using:

-Apply veneer, using minimal wood glue, and spread as thinly as possible with a sponge. This is key, especially with the grain patterns of the veneer i'm using. Too much glue and its possible some areas of the veneer become saturated with glue and will then not take any stain or dye. Ensure its as well clamped as possible, and extra glue around the edges is wiped up, or this will make cutting it harder when the glue dries.

-Cut the excess, sand the edges, and VERY light sanding over the veneer to reduce any higher bits of grain. Again, too much and you hit glue and again the stain wont take.

-Apply cellulose sanding sealer, well shook but a thin coat to prevent further imperfections.

-Again VERY light sanding or you risk removing the stain- this even happened with Liberon spirit dye.

- Apply several coats of lacquer before even thinking about sanding. And again, sand VERY lightly after a few coats and build up some more.

With the above you can fill all the grain and achieve a flat finish. It is very time consuming, but apparently not as much as with poly varnish! At least with car lacquer you can be sure a coat is 100% set after 1 day.

[Uncle Bulgaria]

This struck me on reading your post: did you consider getting the right finish before applying the veneer? Then there would be no trouble with glue take-up preventing stain take-up. I've not stained veneer so only have experience with varnish and oil.

If you apply the veneer subsequently, probably cut to size before the staining, then I would imagine the touch-up finishing would be rather easier.

[PsychMan]

Originally Posted by Uncle Bulgaria

This struck me on reading your post: did you consider getting the right finish before applying the veneer? Then there would be no trouble with glue take-up preventing stain take-up. I've not stained veneer so only have experience with varnish and oil.

If you apply the veneer subsequently, probably cut to size before the staining, then I would imagine the touch-up finishing would be rather easier.

Ah you mean apply the stain before gluing the veneer on? If so, that didn't really occur to me. Though I guess its possible and could help. The only disadvantage I can think of is not really being able to sand after application.

[Uncle Bulgaria]

Yes, if you're having trouble with the glue soaking into the veneer from the back and sealing the grain so the stain doesn't penetrate from the front. You could stain, sand and seal to your heart's content before attaching the veneer. You'd only have the edges to touch up if you hadn't pre-trimmed it, I would imagine. A final clear coat on top would even out the finish.

[David G4EBT]

Sorry to hear of your continued hassles.

Just for future information, I don’t know how aware forum members are about the availability of iron-on veneer, which saves the hassle of glueing. Some members may have used iron on edging for ‘Conti-Board’ veneered chipboard, which is the only iron-on product I’ve had experience of, and it adheres very well.

Here’s one example of a company which supplies a variety of iron-on veneers:

https://www.veneersonline.co.uk/coll...-veneer-sheets

There are several options for glueing veneers, most of which have no doubt been used at one time or another by members. That includes coating both the veneer and the surface to which is to be applied with PVA glue and allowing it to dry, then to iron on the veneer, which causes the PVA to melt. I’ve no personal experience of that. If I have small pieces of veneer to fit, I use ‘Titebond Original’ which I also use for general woodworking. (It tends in woodworking circles to be known as ‘yeller’ due to its colour, albeit it dried colourless). For larger areas, I use hide glue, which I think most people will think is too much of a faff, but it’s what we were taught to do back in the 50’s in woodworking lessons at school and old habits die hard.

As I said earlier, I’ve always use spirit stains which have very low surface tension and penetrate really well as compared to water based stains, and I’ve never had a problem with staining veneer, other than making sure that the shade is what I wanted. Sometimes the title doesn’t correspond with the test result, especially with. Mahogany comes in veteran varieties which can vary from almost red to dark brown. Dark Oak, Walnut and Ebony can all turn out to be very similar.

Every good wish in your endeavours.

[PsychMan]

Thanks as ever David, and the box in the pictures you added looks great!

I wouldn't say "hassles" so much, its all learning for me, but I will repeat until Ive got the method down!

I already have the veneer so stick-ons aren't an option.

With regards the glue bleeding through to the veneers surface, I think one issue I am facing is the glue Im using (in the attached picture), sits in a cold workshop and is quite thick when I come to use it, so despite best efforts to apply a thin layer with a sponge, it is still a challenge. What I might try is keeping it in the house to warm it up, and possibly thin it out a bit with water so I can apply a thinner layer.

[Ambientnoise]

Just to add to the comments about glue, you can get iron-on, hot melt glue in very thin sheets with peel-off backing paper, for when the veneer is glue-less. Makes things quite easy in many ways. You can even find it on Amazon, sold by the sq metre.