Veneer advice for a newbie

[Neocleous]

Hi all,

I am going to veneer some Ash to fairly large MDF boards 900mm x 350mm and 1400mm x 800mm for the first time and I have some stupid questions.

From what I have seen online people seem to use general purpose wood glue or something like Titebond cold press glue.

I don't have a vacuum bag and pump unfortunately, so I am concerned about doing a decent job with PVA type glues as all I have are sheets of MDF or melamine to stack on top.

Can I use contact adhesive to do this? From what I have read this seem to be the glue of choice on curved surfaces any reason why it is not the preferred method for flat boards?

Thanks

 

[Normancb]

Most veneering gurus say that contact adhesive is a no-no for raw wood veneer but OK for backed veneers, Lincoln in the "bible" discusses how to use it (in industry). The only convincing reason I've seen is that the rubber adhesive layer can be affected by solvents from subsequent finishes. I guess the thin layer of veneer doesn't do a lot to keep oxygen away from the rubber adhesive layer which might oxidise over time, go brittle and lose grip, but I've not seen it happen.

You can veneer any area you like using the old hot hide glue way of doing it - a bit messy and needs a bit of practice but needs no clamps or cauls and is easy when you get the hang of it,

I've had good results on big areas using hot-melt glue film - just need to be careful not to over heat it

 

[Neocleous]

Most veneering gurus say that contact adhesive is a no-no for raw wood veneer but OK for backed veneers, Lincoln in the "bible" discusses how to use it (in industry). The only convincing reason I've seen is that the rubber adhesive layer can be affected by solvents from subsequent finishes. I guess the thin layer of veneer doesn't do a lot to keep oxygen away from the rubber adhesive layer which might oxidise over time, go brittle and lose grip, but I've not seen it happen.

You can veneer any area you like using the old hot hide glue way of doing it - a bit messy and needs a bit of practice but needs no clamps or cauls and is easy when you get the hang of it,

I've had good results on big areas using hot-melt glue film - just need to be careful not to over heat it

Thanks for the response, I've just nipped out to Axminster and bought some cold press glue, whether I needed it or not is debatable however for the £15 it cost it wasn't worth the time and material risk of it going wrong.

I have a large MFT so I'll make some cauls and clamp it all to the bench and see what happens...

 

[Neocleous]

Well I’ve given it a go, let’s see how this turns out tomorrow!

 

[Droogs]

did you use flat or curved cauls? ideally you want a slight curve on the bottom of the caul so that as you tighten it down it spreads an even pressure across the board. Otherwise you may starve the joint towards the middle of the board leading to failure fairly quickly after assembly

 

[Neocleous]

did you use flat or curved cauls? ideally you want a slight curve on the bottom of the caul so that as you tighten it down it spreads an even pressure across the board. Otherwise you may starve the joint towards the middle of the board leading to failure fairly quickly after assembly

You can’t really see in the pictures but I ironed on a couple of pieces of edge banding to the MDF strips to spread the pressure from the middle to the edges.

 

[Normancb]

Let us know how you get on. The manufacturers recommend 100 - 250 psi clamping pressure for that glue

 

[Neocleous]

One turned out ok the other is a little wrinkly, I think I used too much glue on the wrinkly panel.

I applied some heat to it with an iron to try and smooth it out and put it back in the clamps but I have haven’t checked on it yet

I can see how a vacuum bag would make much easier work on larger panels much easier and consistent.

 

[Neocleous]

So the top panel is still a bit wrinkly which is a shame however I learned a lot from this.

1. Thin even coat of glue is essential
2. Over size the board to the veneer rather than veneer to the board, the delicate edges of the veneer are very difficult to handle compared to an mdf board
3. I don’t have enough clamps for a larger glue up

 

[Neocleous]

I was having a look on easy composites and they have a starter kit available. There is a video on that page where they demonstrate using a domestic vacuum bag that people use to pack clothes away with. Has anyone ever given that a go for woodworking?

Vacuum Bagging Starter Kit - Easy Composites

I know the pumps for proper vacuum lamination pull about 80% vacuum but I wonder if you can get close with a clothes bag?

 

[XTiffy]

For what you are trying to do I would use the iron-on glue film. Though I agree with the quote about using scotch glue, that does need a lot of practice for the sizes you quote. Also you have to work fast to be able to squeze out excess glue, not for the faint hearted. The problem with contact glue is one of getting the veneer down flat (it tends to have high spots if the glue isn't absolutely even).

 

[recipio]

Veneering looks easy until you try it . You can use contact adhesive on paper backed veneer but it should be the gel type to avoid ' rubbery bits ' in the adhesive. It is not reliable for standard veneer. If you don't have a vacuum press then the method you have used is fine. I like to make life easy and have bought a set of ' welder's clamps which will reach 60 cm or so into the center of a panel. I use some 12 mm ply panels laid on a yoga mat to distribute the pressure and leave overnight to set. Titebond cold press is excellent and only needs a thin coat as you say. If you get any bleed through the veneer it will sand off easily unlike other PVA glues.
Considering a vacuum press will draw about 8.5 tons/ sq meter of pressure I doubt if a clothes bag will do anything close to that. Veneering is a long learning curve !.

 

[Neocleous]

Veneering looks easy until you try it . You can use contact adhesive on paper backed veneer but it should be the gel type to avoid ' rubbery bits ' in the adhesive. It is not reliable for standard veneer. If you don't have a vacuum press then the method you have used is fine. I like to make life easy and have bought a set of ' welder's clamps which will reach 60 cm or so into the center of a panel. I use some 12 mm ply panels laid on a yoga mat to distribute the pressure and leave overnight to set. Titebond cold press is excellent and only needs a thin coat as you say. If you get any bleed through the veneer it will sand off easily unlike other PVA glues.
Considering a vacuum press will draw about 8.5 tons/ sq meter of pressure I doubt if a clothes bag will do anything close to that. Veneering is a long learning curve !.

Wishful thinking I know! This is not a cheap hobby!

I think I will go down the holt melt film approach as the large panel isn’t going to work well with the set up I have at the moment.
Glue Film, Glue Film Iron On, Hot Melt Adhesive, Heat Activated Adhesive, Glue Film For Veneering

 

[Droogs]

Depending on the size of the piece being done, I use a mix of methods. For largish bits, I use my proper vacuum pump which is set up with 2 x fire extinguishers between it and the work. They have valves that allow me to bring them to vacuum first and allow rapid air removal from the bag when opened. For smaller bits I actually use a food vacuum bag sealer and this works well enough for £20 from lidl. and for complicated work I use the old methods of hide glue hot sandbags and heated plattens.

 

[recipio]

Wishful thinking I know! This is not a cheap hobby!

I think I will go down the holt melt film approach as the large panel isn’t going to work well with the set up I have at the moment.
Glue Film, Glue Film Iron On, Hot Melt Adhesive, Heat Activated Adhesive, Glue Film For Veneering

It works but is a bit finnicky. I bought ten meters of the stuff a few years ago but found it refused to melt. Cranking up the heat wasn't the answer either as the joints shrank leaving gaps. Try a small sample first to test it's quality.

 

[HOJ]

I am going to veneer some Ash to fairly large MDF boards 900mm x 350mm and 1400mm x 800mm for the first time

I am curios as to why you didn't just buy a sheet of Ash veneered MDF, would it not have been more cost effective, I do veneer work, (I use an Airpress system) but only if I can warrant the overall benefit financially, not just to me but my client.

 

[worn thumbs]

It is entirely possible to use contact adhesive and a veneer hammer to do the job.If you don't possess a veneer hammer,it isn't a huge task to make one.

 

[Neocleous]

I am curios as to why you didn't just buy a sheet of Ash veneered MDF, would it not have been more cost effective, I do veneer work, (I use an Airpress system) but only if I can warrant the overall benefit financially, not just to me but my client.

I was using some scraps that I had and I realised after I started that I didn't have quite enough for the end panels and decided that rather than buy another sheet and ending up with a lot left over I would give veneering a go as it didn't seem that difficult, plus the fact that the large back panel is 6mm thick which I can't get hold of in my area any way.

Suffice to say I would usually buy pre veneered panels.