Veneering - Issues with (what appears to be) Mould

[Puggers]

Hi,
Odd one for me this as whilst I’ve used veneers many times to primarily make boxes, I’ve never come across the product developing a mould type appearance when removing from the manual press.
On this occasion I’ve applied Karelian birch on 6mm MRMDF using Titebond cold press glue.
The piece was sandwiched between a piece of grease proof/wax paper each side to help with any squeeze out through the veneer which is very decorative.
I’ve used this practise time and again with no issues but on this occasion there’s some dark green to black spotting on the veneer and larger areas where the grain pattern is particularly curly.
I have spare veneer to complete the box but has anyone else come across this before or have any guidance on what I could do to avoid a possible repetition?
Thanks in advance.

 

[MARK.B.]

Could you post a picture please Puggers, it may help those that know more about these things than i do

 

[Droogs]

Your birch when it was alive has obviously had a proliferation of lichen. This is a symbiotic organism made up of a fungus (which retains moisture) and an algae which feeds on the moisture and with clean air and good sunlight produces waste in a form that the fungus uses for food. It is completely harmless to the tree and the wood but can result in a greenish tinge to the wood of the tree (comes from a green slime on the tree bark). I would suggest you treat the rest of your veneer flitch with a copper sulfate solution to truly kill any of the organisms that may be in stasis in the wood of the veneer. It would seem to have reacted to the water in your glue and the warm of the chemical reaction as it set and given you a present.

Once you have treated the rest of the veneer allow it to dry and then give it a quick wipe with IPA to see if the fungus has stained any of the rest of the wood. If so you can bleach it out but some staining may remain. Treat the veneer with restorer/softner and store in a cool place.

 

[Puggers]

Photos hopefully now attached and clear.
I should add that I always use a small piece of around 3” x 3” as a tester and there were no issues which is why I’m somewhat baffled.

 

[Puggers]

@Droogs, thanks for taking the time to reply so quickly and for the useful advice.
I don’t think I’ll ever get to the bottom of why one side of the glued-up board was fine and the other affected so much despite running consecutively from the same flitch but given it’s a natural product, it’s obviously done what nature does!
I’ve plenty enough to go through the method you’ve suggested so I’ll see what happens and report back.
Thanks again

 

[baldkev]

Great reply from @Droogs
Im still learning!

Im struggled a bit with the ipa reference, i know it wasnt going to be brew dog punk but i had to google it

 

[the great waldo]

I'm not sure if I would use copper sulphate as its green, Maybe hydrogen peroxide would be a reasonable alternative and easily available.
Cheers
Andrew

 

[Alasdair]

You could try BAC50. I normally use it for moss/lichen control on exterior timber. Its clear but not sure if it would leave staining. I get it from Benzalkonium Chloride - Alkyl Dimethyl Benzyl Ammonium Chloride - BAC 50
Alasdair

 

[Peter Sefton]

I have seen this once many moons ago but to a lesser degree in some maple or sycamore veneered work.

I would play with the panels you have already veneered, first try some weak household bleach wash over the panel to see if it helps-my guess is it won't. Then on a fresh panel try oxalic acid or peroxide to see if that removes it.

As Droogs says I would think the veneer has something in it and the moisture is awakening it, I am sure you have been careful but dirty veneering equipment can cause problems. I have also seen issues when veneer softening agents are used I believe the glycerine can induce mould so proceed with caution.

The West System may work as it's not water based but I have found does sometimes have reactions with other veneers-it turned some elm black once.

 

[Spectric]

I believe the glycerine can induce mould

Just like a petri dish except you do not want to induce mold growth.

 

[Droogs]

I'm not sure if I would use copper sulphate as its green, Maybe hydrogen peroxide would be a reasonable alternative and easily available.
Cheers
Andrew

Copper sulphate is used to clean off and kill lichen growth on growing trees, it is the sullphur that is the active part in this process. It is done to trees that are known to intended to use for veneering or for show work in the future. It is a strange thing that this is fairly well known in arboreal circles but nearly unknown in the world of cutty & choppy up wood.


edit
oh and as @Peter Sefton said above by bleaching, I didn't mean house bleach but oxalic acid as used to bleach wood to lighten/draw out the colour from stains etc

 

[recipio]

Its definitely mould. I use Masur birch with Titebond cold veneer glue and thankfully have not had this problem. However I cut up a camping mat - the type with foam and a silvered side and put that on the veneer as this will distribute the pressure. I presume you are not flattening the veneer with damp paper prior to glueing as this will obviously encourage mould growth. ? I certainly get a green mould on Baltic Ply after about a year and its a beggar to remove.

 

[Puggers]

Thanks to all for the ongoing replies -
@the great waldo - I have some hydrogen peroxide so, yes I can try that.
@Alasdair - BAC50 isn’t something I’m familiar with but I’ll read more into this.
@Peter Sefton - I’d certainty like to see if the board can be treated and fortunately (in a perverse way) it’s large enough to try various options.
If these don’t work, I’ll at least learn something for the future but I also appreciate why you’ve mentioned the cleanliness of the equipment and I am satisfied I cleaned and then placed the veneer onto grease proof/wax paper which was then in contact with the clamping mat followed by the boards.
@Droogs - understood; I’ve had very limited use of oxalic in other maters and am sure I’ve some stored away (use by date….if appropriate?)
@recipio - no, definitely not flattened in that manner as what you say would make sense.
On the basis that you’ve used Titebond too, do you think there’s benefit after trying the other options suggested above in applying the veneer with an impact glue instead?
I don’t think the Titebond was contributing to drawing any mould out but as I’ve enough scraps, it might be worth a quick experiment before I dive back in with the Titebond

 

[recipio]

@recipio[/USER] - no, definitely not flattened in that manner as what you say would make sense.
On the basis that you’ve used Titebond too, do you think there’s benefit after trying the other options suggested above in applying the veneer with an impact glue instead?
I don’t think the Titebond was contributing to drawing any mould out but as I’ve enough scraps, it might be worth a quick experiment before I dive back in with the Titebond

I wouldn't try impact adhesive on regular veneer - it's likely to lift at the edges. The Titebond is the best glue I've found for veneering. The trick is to brush it on with a silicone brush which leaves a ridged surface - a bit like adhesive for tiles ! I also find that it is not foolproof - it will leach through most veneers if applied too heavily but will sand off easily when dry. It might be worth trying the veneer on regular MDF- the MRMDF will repel moisture and dare I say has a green tint on the surface.?

 

[Puggers]

@recipio, thanks. Before switching to Titebond, I’d used impact before with rebated panel lids quite some while ago without issue of lifting (if there was, it would have been hidden) but I was more wondering whether it could mitigate any possibility that the Titebond could have contributed to moisture drawing out the mould.
Given it was only in a couple of areas of the panel, I doubted it but it was worth checking your experience with impact.
Similar to the MRMDF leaching too, I couldn’t rule it out but, again given it was in limited areas, my thought was it’s unlikely and hasn’t happened before.
I’ve plenty of standard MDF and ply so I think as I’ll be using this veneer more frequently, I’ll do some experimenting with the offcuts and using all of the great prep’ suggestions already offered and with different substrates.
I’ll report back in a week or so in case it helps anyone else in the future.