Adhesive bleed-through is a common and frustrating occurrence when bonding timber veneers, especially on wood species like Oak.

If unaddressed, it can ruin the veneer’s look, leaving it shabby and unprofessional. 

With decades of adhesive experience under our belt, Adkwik has compiled an article of tips and techniques for preventing adhesive bleed-through.

In this piece, we’ll delve into the root cause of the problem, explain why it happens, and provide practical solutions that can save you time, money, and stress.

The Problem: Adhesive Bleed Through

What is adhesive bleed-through?

Adhesive bleed-through occurs when glue seeps through the pores of the timber veneer and shows up on the surface of the panel. 

This issue can lead to finishing problems and an unflattering result; neither outcome is desirable in a professional occupation.

What does adhesive bleed-through look like?

Although often clear, sometimes the adhesive appears in grey or silver flecks on the surface, which are only exaggerated when the veneer is polished, lacquered or stained. Below is an image that highlights this issue.

Explanation: Why Does This Happen?

The type of timber, adhesive and amount of pressure can all affect bleed-through.

Here’s all you need to know about each factor, so you can be aware of how and why this issue occurs.

How timber can affect bleed through.

Some timber veneers are incredibly porous and have large open fibres or cells, which make it easier for the adhesive to seep through. These gaps are often invisible to the naked eye.  

Hence, porous timbers, such as Oak, Burr, and dark or fumed veneers, like Wenge or Walnut, are more susceptible to bleeding through.

Thin veneer panels are also prone to bleed through as the adhesive can quickly saturate and seep through the wood. 

You can still use this timber successfully, but be aware of its vulnerability.

How adhesive can affect bleed-through:

Urea Formaldehyde Resins and PVA adhesives are the top choices for bonding timber veneers. However, they are still liable to bleed through – particularly if misapplied. 

Applying too much glue or spreading it unevenly can increase the risk of adhesive bleeding or overflowing from the veneer’s edges.

How the amount of pressure can affect bleed-through:

Too much pressure on the veneer during the bonding process can force the adhesive through the fibres, creating a messy result. 

Solution: How to Prevent Adhesive Bleed Through

Each individual has their way of resolving adhesive bleed-through, albeit time-consuming. 

Many don’t realise that you can nearly sidestep this issue altogether by making a few tweaks and taking extra precautions, particularly when applying the correct adhesive.

Use hardeners and extenders to thicken the adhesive. 

Often this problem can be alleviated or prevented by using hardeners or extenders to thicken the veneer.

A successful combination of products is the Prefere 4152 resin mixed with an appropriate hardener for either a cold or hot press, then combined with a Prefere 5912 extender. Always adhere to the mix ratio suggested in the product details.

Cold Press Powder Hardeners:

Prefere 5600

Prefere 5689

Hot Press Powder Hardeners:

These hot press powder hardeners require press temperatures of 80°C. 

Prefere 5611

Coat the veneer with an even application of adhesive.

You can apply resin adhesive with a brush, spreader or a mechanical glue roller. We recommend rolling out the adhesive to give the board an even but sufficient coat.

Browse Adkwik’s complete collection of adhesive applicators for different ways to apply adhesive and obtain spare or replacement parts. 

Disguise bleed-through with resin pigment. 

Suppose adhesive continues to penetrate the surface of the veneer. In that case, you can add a brown or white Prefere pigment tint to the Prefere resin to cleverly disguise any apparent defects.

Results: A Professional Finish

Taking these steps should virtually eradicate the bleed-through, resulting in less product wastage and saving your business time and money. Overall, you can streamline your production and see a genuine improvement in results. 

For example, in one of our recent projects, we offered adhesive expertise to a specialist manufacturer of fire and security doors. 

As a result of a few simple changes, including an accurate coat weight of the adhesive, we reduced press times and material costs, increased throughput, and nearly eliminated the door panel’s imperfections.

The company’s customers are equally delighted with the quality of the doors.

You can read further into this case in our ‘Improving Adhesive Bonding Processes Increases Production For Specialist Manufacturer’ article.

Contact Adkwik

If you’re experiencing issues with adhesive bleed-through when bonding timber veneers, reach out to the Adkwik team.

You can contact us at 01223 737091, via our live chat or by dropping a message via our online contact form.