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Old 23rd October 2006, 09:16 AM   #1
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Default Veneering methods

Hello,

I am about to start my first speaker project and have been researching veneering methods. Unfortunately I have not been able to come to any conclusions on the best method. My concerns are not just ease of use but I also want to ensure it will stand the test of time. I will be using raw 0.6mm American black walnut.

Contact Adhesive:
Some people say it has no place in a good workshop, some say cabinet makers use it?? I have heard it should never be used with raw veneer but don't know why???
I have done a few trials with scraps of veneer on MDF and the results look good. My only concern is longevity but I have used it to glue the melamine edging on my kitchen worktops and it has held a very secure joint for 7-8 years with no problems.

PVA Iron on method:
I have done a couple of trials but had problems with this method. I found it bonded strongly in some places but not in others especially ay the edges of the MDF, not sure what I'm doing wrong.

I have also seen glue film http://www.valeveneers.co.uk/ad.html in a couple of places in the UK but have not seen many opinions on it's suitability. Does anyone have any experience of this stuff?

Any advice would be much appreciated. As I said above my main concern is if I am going to invest a lot of time and money I want the results to last without worrying about bubbling or peeling.

Cheers Kenny.
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Old 29th October 2006, 04:01 PM   #2
oldfart is offline oldfart  Australia
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Default Veneering

Hello Kenny,
I lecture in traditional cabinetmaking, which also includes hand veneering, so I hope this information will assist you in your project.
Real wood veneer can be laid up using contact adhesive -- but ONLY if you have access to a daylight press or vacumn press, if not, leave contact adhesives alone, thay can be bad news.
PVA glue, particularlily the Aliphatic type (yellow) can be used, it is applied with a sponge roller to the substrate ( MDF, ply etc) but still needs a press, however a vacumn bag can be used on flat panel sides, but not easily on a complete box, an ordinary vacumn cleaner (used on suck not blow LOL) can evacuate sufficient air to press the surfaces during the setting time of PVA, about 2hrs min, less in warmer climates.
However my prefered method is the old time trusted use of scotch glue also know as pearl glue, animal glue or protein glue, it is extracted from animal bones, the gelatin from the marrow etc of bones. It is smelly an a bit messy but it sticks like phoo to an army blanket.
It has to be heated in a double boiler and thinned to run from the brush freely, hot and thin is the way to go, a generous coating is applied to the veneer and the MDF and then the veneer is laid using an old fashion electric iron (non-steam type) the veneer is heated by the irons heat and the veneer is worked over from the centre to the edges to remove excess glue and bring the veneer into close contact with the MDF. The iron should be at about the temp of boiling water 212f or a little above, spit on it if it hisses its TO HOT, a piece of 1/4 inch thick by 2" X 4" acrylic will make a good tool to use to squeegee the excess hot glue from under the veneer , clean up of excess glue is by hot water, but do not get the veneer too wet, a damp cloth wiped over the veneer while heating will help the process, it can also be weight down by another flat board with weights on eg house bricks etc, but plce clean paper between the veneer and any board placed on top. Leave to cool and set over night. Its Late here so I will finish this post in the next couple of days .

Regards Gary.
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Old 29th October 2006, 10:27 PM   #3
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Oldfart, tell us more. I have yet to try your prefered method, but I think I'm going to give it a shot. I would love to hear more, and I know there are a lot out there that would also.

This question pops up on a regular basis, it's good to have some one that really knows aboard.


PS. Noticed your sig, Perth land of sun and flies. I was in Exmouth for a year and a half. When I first got there and was talking to some folks inside the local pub, they were gesturing their hands in front of their face as if they were swatting flies. I began to wonder if all Aussies where a tad touched. After a few weeks in fly country, I caught myself indoors, no flies and doing the same thing.
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Old 31st October 2006, 02:23 PM   #4
kec is offline kec  United States
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Wow Oldfart, that's a lot of work. I'm sure it works real well.

I simply use the PVA method - applied to the MDF only (non-paper backed veneer) with a small foam roller. I use cauls lined with 1/16" foam sheets from Michael's (craft store) wrapped with packaging tape (to prevent sticking). Then lots of quick clamps.

It works very well, but you do have to be quick with the clamps and it helps if you do it in cool weather - to prevent the glue from drying too quick. You also have to make sure you put the right amount of glue down - not too little and not too much or it will come through the grain. This is where practice on test pieces helps. So far, no lifted veneer.

I would also suggest not to use contact cement. If you apply it to raw veneer it will bleed through, thus preventing you from applying a nice finish. Plus, contact cement never dries hard, it remains rubbery.


Other things to consider:

I miter the cabinet joints which works best for veneering. If you use a butt joint the end grain can soak up too much glue too fast and the veneer may not bond correctly. The exception is the back of the cabinet. I do a 1/2" dado (on 3/4" MDF) which minimizes the amount of end grain shown (1/4").

I also make my cabinets with a removable baffle which helps aid in the clamping process. I can usually do 2 sides at a time.


-Ken
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Old 31st October 2006, 03:43 PM   #5
oldfart is offline oldfart  Australia
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Default Veneer PT-2 (of many lol)

Hi Dryseals -- its called the Ozzie Salute -- Fly Swattin LOL.
Ok, now to enlarge on the methods to lay real wood veneers to MDF, plywood and any solid timber.
Before continuing to describe my prefered method of using animal glue to lay veneer there are a couple of other glues that deserve mention, firstly urea formaldehyde, a very strong, waterproof, two part glue it also however requires a decent press setup, or vacumn bag. It is like most modern glues, expensive in small quantities. It has a reasonable pot life if stored properly, one mixed it has an open time of about 10mins - varies with ambient temperature though.
Cascamite -- sold in UK now under the name of Extramite, very strong, waterproof, made from milk by product, also contains formaldehyde. it used by small boat builders ,( I also use it for my offshore racing boat models, up to 8 FOOT length, powered by 180cc modified 2 stroke motors HEHEEHEE I go for broke with my models LOL, I also veneer my diagonal planked hulls with hard mahogany veneer, I dont like Plastic Fantistics, Gimme real wood any day . I DO NOT USE A PRESS TO VENEER THE CURVED HULLS -- I heat the strips of glued veneer with an old style iron, took a while to get it right though, so I do not recommended the process as a first option.

The biggest drawback with ALL modern glues is that thay will stain or leave areas of the veneer impervious to all types of stain including hydrocarbon, oil, water or pigment stains, so great care must be taken to not allow any of these glues to come into contact with the face of the veneer, even PVA, which is water soluable in its liquid state merely spreads in a thin wash when cleaned off with water, however if you have a very thick veneer of .8MM or more the surface can be cleaned up with a cabinet scraper (old school again lol) , do not reach for the electric sander though, PVA is also thermoplastic, the heat from sanding will only serve to drive it further into the grain, BAD NEWS BABY, oh phoo do I really want all this grief, dont dispair, it should get better from now on errrr umm honest.
So now lets continue with MY prefered option of laying veneers with good old, smelly sticky and most importantly REVERSIBLE animal glue -- Reversible? You ask, yes it is the ONLY glue that allows you to remove the veneer if you make a faux par,( stuff up, dogs dinner, a right mess or b***s up, c**k up , no LOL there though). By carefully using moisture from a damp cloth under the iron veneer glued with animal glue can be removed and relaid, needs a bit a practice though, so go carefull.
A press is not needed, but a heated caul can be of help ( More on cauls later )
Surface preparation prior to glueing any substrate ( MDF, ply etc) MDF has a very smoth almost case hardened shiny surface, not the best for any glue, so first KEY the surface by using a 180 grit garnet or silicia abrasive paper, NOT with a power sander though, this is twin armstrong land, and I'm a Ludite, an I dont like noisy machines in my workshop, cant hear me music above them electickery thingies lol. Sand diagonally across the grain to the left and right, or more technickelly, perpendicular to the precedding direction, just enough to produce visible scratches in the surface, dont overdo it.
Most surfaces benefit from a size coat of the animal glue, thinned to the consistency of 3in1 oil, sewing machineoil , not sure of its SAE number, but most if not all will know what I'm gettin at.
Whoopps I better get this in the right order --
Animal glue preparation --
Place sufficent granulated or pearl animal glue in a clean plastic or ceramic ( mug cup) and cover with COLD water, hot water will turn it into a big sticky lump that defies description, hheheheh, been there done that, but learnt the lesson real quick.
When the glue has absorbed the water, swollen and become rubbery, it is then heated in a double boiler ( a saucepan of simmering water in which to float the plasic container of glue, the glue container MUST NOT sit on the bottom of the pan, and DO NOT heat directly the container of glue, gee it dont alf pong when it burns an it isnt fit for dippin toffee apples into either.
The glue will slowly melt, as it deos add only a small amount of water to assist in it becomeing thin enough to use, allow to heat in the simmering water, DO NOT boil it or it will lose some of its strength, it is ready to use when it runs from the brush freely, do not use this glue if it is too thick, add more water until it is fairly runny. You do not need to make new batches of glue, merely add more pre-soaked glue as needed. BUT NOT a year later, thats pushing yer luck lol.
I'm enjoying a rather nice bottle of Port . it's gettin late an I got a mob of first year apprentices to teach tomorow, so I'd better go before I slide outa my seat giggle burp. Parts 3 to 233671019 will follow during the next few days.
Oh as a side benifit you cant get high from sniffing Animal glue, you only end up smelling like a dead animal, keeps the girls away when we are doing those important things us mere males must do ehheh.
Regards from Gary
P.S Kenny, I used to live in Dorset U.K but the weather got me down , so I emigrated to OZ, you live in a rather unique area, great fishing off the coast around there, but a bit too cold for me now, I have got a bit soft in the beaut weather here lol.
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Old 1st November 2006, 01:23 PM   #6
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Hi guys,

Thanks for the replys, especially your very detailed description Oldfart. I'm not quite ready for the veneering yet so I have time to do a few practices. Hopefully It will be a sucess.

You're right I'm in a very remote area and the weather is poor but you get used to it.

Cheers Kenny
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Old 1st November 2006, 03:11 PM   #7
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I personally use contact cement, BUT not with raw veneer. Not only do you have to worry about bleed thru but if you apply a stain or clear coat it could cause the contact cement to release from the veneer. I only use backed veneer, either paper or some of the 22mil no seam stuff. Have never had a problem with contact cement using either of these. Everyone has there methods such as oldfart, whose methods are tried and true by us woodworkers. If you use contact cement, use the original formula not the water based stuff. Good luck
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Old 1st November 2006, 04:28 PM   #8
oldfart is offline oldfart  Australia
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Default Veneering -- cont

Hello KEC (Ken)
Yes contact adhesive is BAD news -- particularly when it goes wrong, however it can be removed with a non-caustic paint stripper. Useing ACETONE or contact adhesive thinners merely spreads it about and drives it further into the grain or surface of MDF.
Mitering the sides together minimises the problem of end grain (cut edge) absorbtion problems, however a size coat of thinned PVA does reduce lack of adhesio problems (allow the size coat to dry first though, about 2hrs minium)
Many people may not have the facilities or hand tools to mitre the sides together, so a rebate equal to 2/3 of the material thickness is a good compromise for any chosen glue type, 19mm thick substrate = 12mm rebate, forget the 1mm difference, lol, its near enough.
Glue film and pre glued veneer that are heated and ironed down have adhesion problems also, unless you have a heated press or heated vacumn press it is better to avoid them, pre- glued edging strips up to 25mm wide can be laid with an ordinary domestic iron, but success is not guaranteed. Edges are better faced with solid timber about 1/4" thick (6mm) clamped and glued, not pinned and glued, then lay your chosen veneer over the solid edge.
Sorry Guys and Gals,-- yes I do it the hard way, but it works, veneer is not cheap, nor is the time you invest in your designs, and you gotta live with it, so do yourselves a favour and and enjoy doing it as well as you are able.
Industry uses RF heating to cure their glues under pressure, and us mere mortals aint got access to that technology. unless we are very lucky.
Modern glues wait for no man or woman (musn't forget the ladies who have equal status in all matters, what would we do without them, MMMMM --- Oh dear I might have inadvertanly pushed some peoples buttons on that comment, but its not a new topic that has any bearing on this forum) so prepare all the necessary equipment before you start to lay your veneers, or you will find yourselves in a state of panic as the glue cures before your eyes, not a pretty sight as a person falls apart at the disaster happening before them.
If you are new to veneering avoid open gain timbers like Oak, particularly American White Oak, American Red Oak, English Oak,European Oak , Japanes Oak and Australian Jarrah they have a very high cross grain expansion rate with any water based glue, when they shrink it can cause joint failure even on mitered carcuses.

In my last post I mentioned a glue called Cascamite (now known and sold under the name of Extramite in the U.K) it is mixed with water, and clean up , while still wet is by water, this is a very strong glue and is excellent for all internal bracing and case construction, it is also much cheaper than all two part glues, it was used in airframe construction of many timber framed aircraft during the 2nd WW, so it has stood the test of time, it is also waterproof and used in small boat construction, it is sold as a powder and if stored in airtight containers has a shelf life of about 2yrs max, after that cure time starts to increase , if hard lumps start to form in the dry product it is near the end of its usable life.
Time for bed, then tomorrow I can play with wood again, gee what would we do without wood, I do not want to even ponder on that thought. Metal violins or oboes, NOOOOOOO. LOL.
Good night all,
Regards Gary.
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Old 2nd November 2006, 09:13 AM   #9
fgroen is offline fgroen  Netherlands
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I use the PVA - iron method to great satisfaction. Best results are obtained when you start ironing after the glue is just dry, and still a bit damp.

I had one surface of my speakers where I applied glue and let it dry too long. In fact, after applying glue I had no time to vineer directly when dried, but only two days later. It still worked, but it was very hard to get a good bond.

Looked at the animal glue as well, but never gave it a shot. It seemed a bit too labour intensive for me. I totally get that it will provide the most reliable bond, and the old-fashioned workmanship that goes with it definately has it's charm.

However, I was a bit more pragmatic about vineering, and I don't regret the result:

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Old 2nd November 2006, 11:00 AM   #10
es44 is offline es44  Denmark
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Quote:
Originally posted by fgroen
[B]I use the PVA - iron method to great satisfaction. Best results are obtained when you start ironing after the glue is just dry, and still a bit damp.

Do you allow the veneer to dry a little bit before you put it on the MDF and iron it, or do you put it directly on the MDF, and then let dry a little before ironing ?


However, I was a bit more pragmatic about vineering, and I don't regret the result:

You have absolutely nothing to regret... WauW they look nice

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