Adhesive for glass and wood, advice required please

[Howie]

Hi

I have a project starting for some TV room units that incorporate glass quite heavily into the design.

The units are being made of a mix of MDF and MDF veneer to which I will be adding 6mm rebates (about 30 mm deep) to some edges and then sticking 6mm toughened glass onto the rebates in the same plane. ie. it becomes one surface of MDF and glass. There will be some degree of structural integrity required of the bond but not too major.

The question I have for you knowledgable lot is this:

The glass will show at points where it has been stuck and I wish the adhesive to therefore be clear behind and not show. I ideally would like the adhesive to have some degree of viscosity to ensure a good bond.

Any advice or questions to clarify my quandary about this would be greatly appreciated.

thanks

Howie

 

[dickm]

No ideas myself, but if you don't get any suitable suggestions, I could ask my daughter in the US. Her whole job is sorting out adhesives to stick glass to things and things to glass in vehicles.

 

[Jonzjob]

When I have had to stick glass to wooden glazed exterior French doors I used silicon. The glass was on the inner flat face of the doors. I just held it in place with glazing sprigs and a bead of silicon around the outside. When the silicon had cured, about 24 hours, the sprigs were removed and the only way that glass was going to come off was ti cut the silicon off of it.

That way you could use clear, good quality, silicon on the recess press the glass onto it and I don't think it would move and it will also give a bit of flex with the 2 different expansion rates, glass/MDF.

If you think about it, silicon is used to stick glass to glass on some pretty large fish tanks and there wouldn't be any problem onto the MDF.

 

[Howie]

Thanks for the quick replies Dick & John

I think your daughter in the states Dick will probably be using UV activated stuff, a little too ambitious for one guy in a workshop I suspect. Don't count it out though, I am quite keen to deliver a good finish on this furniture.

John, I have considered clear silicon and this may be the answer. Can you see the silicon once set from the glass side? This is because the bond will show in my design and I'm after the "invisible" bond look.

regards
Howie

 

[Jonzjob]

When I did my windows you could see the silicon because it was a bead all the way round the edge, but I would think that if the 6mm glass is set in a 6mm rebate the silicon will be pretty thin and probably unseen. If I were doing it I would give it a trial using a bit of plexiglass, cut the rebate and stick it in?

Or even an odd bit of glass which would be better still. I am sure that if you go to the bloke supplying the glass he would hapily let you have an offcut of 6mm glass to try it? You would only need a small bit :mrgreen:

 

[paultnl]

I would suggest you have a look here http://www.dowcorning.com/?WT.mc_id=25275401&WT.srch=1 for advice on the best silicon for your needs.

 

[jasonB]

Are you going to paint/varnish lacquer the MDF as if using clear you will see the cut edge. If its coated then you need to watch which silicon you use as some will attack paints etc and discolour them after time.

Why not UV activated adhesive, I'm just a guy in a workshop and have farmed it out though that was glass on glass, 18mm thick glass shelves sticking out from a mirror, its strong stuff.

J

 

[Howie]

The sections of MDF that are going to be bonded to the glass will be finished in a oil based eggshell.

A bit worrying to think the silicon may discolour the paint over time. Still better to know the consequences of certain actions which is why I appreciate the knowledge forums like this give.

I have looked on google for possible solutions but to no avail and tried calling my glass guy but he's closed shop for the week.

Howie

 

[Allylearm]

In my shopfitting days to fit drop down wires that halogens lit up displays for jewelry and cosmetics I used good old super glue. That was alloy ferrule to glass. All you did was attached to ceiling or over hanged ceiling and used and drop the fixing cable like a plumb bob, marked the spot on the glass then just stuck the ferrule.

On glass to wood as in glazing I have used silicon.

 

[jasonB]

If its onto eggshell then definately need a neutral cure, talk to your glass man he should have something suitable.

J

 

[Eric The Viking]

Another thing to remember about silicone is that it's a right pumpkin to get off surfaces, not least glass itself, and most finishes won't stick to it.

The 'silicone remover' chemistry basically doesn't. Before it's cured you can get rid of most of it by rubbing with industrial paper towel, then towel dampened with xylene, but it's really hard not to leave sticky streaks.

I can see the value of 'neutral cure,' as normally silicone sweats acetic acid as it solidifies. I presume that would attack paint.

If this glass has to be flush to a surface, that introduces another issue: alignment. You'll need enough rebate depth to take the glue/sealant, but if you do it with the glass horizontal, there's a risk it will drop below the plane surface. Can you do it in two stages: shim/wedge and fix the glass behind (silicone or whatever), then remove shims and seal the crack with more sealant.

I've fitted a TV in one of our bathrooms (it's a girlie thing, so wife and daughters tell me). The glass was done as above: fitted with silicone and shimmed with plastic packers to get an even gap all round with the mosaic tiles (that's a nightmare in its own right!), then grouted to be flush. It looks pretty good.

One other cheat: if the glass has a slight tint, this hides any edges behind pretty well. I painted the inside of the rebate with blackboard paint before fitting, and used clear silicone. Tinted glass in front of a TV improves the contrast at the expense of brightness. Works well in my application - when the glass was delivered it was darker than I expected, but this doesn't matter in practice.

I realise none of the above directly addresses the question, but might be food for thought.

E.

PS: my tiling guy, who's very good, will only use Corning silicone products, as he's had huge problems with other brands failing after a while. I know they do neutral cure, but didn't use it as it wasn't relevant to me at the time.

 

[dickm]

I think your daughter in the states Dick will probably be using UV activated stuff, a little too ambitious for one guy in a workshop I suspect. Don't count it out though, I am quite keen to deliver a good finish on this furniture.

I've summarised your query and some of the responses to herself at Nippon Sheet Glass. Depending on her workload, I'll either get a reply today, or nothing........

 

[Howie]

Hi all

Many thanks for all the responses, it has given me plenty to think about.

It would seem that the majority are recommending neutral cure silicon. So I am going to make a test joint to see if I can get the invisible bond with the strength required.

Also superglue was suggested but feel it won't have enough viscosity to make the all the glass contact with the MDF. Unless I buy a pallet load of the stuff, and then probably most will just end up sticking all my fingers together.

Also Eric's observation about ensuring the glass and MDF surfaces stay in the same plane while bondng is valid. I will be making up a simple jig to hold all the pieces in alignment during the bonding, thanks Eric I probably would not have thought of this until I was knee deep in silicon.

I will take some pictures and post up the results in the near future.

I'm still open to other ideas if anyone has them.

Thanks
Howie

 

[Jonzjob]

Don't put too much strain on the toughened glass or you may finish up with more tiny bits of it than you know what to do with :mrgreen: :mrgreen:

 

[geertswaans]

how about mitre bond.
that is tough and dries clear
Geert

 

[Howie]

Ha ha John, yeah love the idea if it shattering into a thousand or more pieces. Still with winter coming could make a nice jigsaw puzzle to do in the evenings.
I am going to upgrade the glass to 8mm toughened on thinking about it, so will make the rebates 9mm deep to allow for the silicon.

Geert,
Thanks for the thought but it's probably going to lack the viscosity to fill the gaps between the smooth glass and the MDF, which although will be sanded and painted always will be slightly imperfect.

Loving the ideas and responses.

thanks again
Howie

 

[dickm]

Got what looks like a very hastily drafted reply from my oracle in the States:-

How much thermal change could the parts see in use? If not much then an
epoxy would be a good bet (although I've never tested adhesion to MDF
but I would guess that epoxy would work with that). If they will get
very cold (-30 or lower) then stay with a silicone to absorb thermal
expansion mismatch (or spring for 3M DP105 - a very flexible epoxy). To
improve moisture resistance an organosilane primer would help if you can
get hold of those on the open market (Dow, 3M, Sika, and lots of other
people make them).

Dunno whether that helps..........
But I like the idea of the items possibly being in temperatures of -30 or below :roll:

 

[Jonzjob]

Crikey Howie! I yer tele room is going below -30 º Celciheight then I wish yer popcorn good luck, 'cause they guna be like a tad cold? :mrgreen: :mrgreen: :ho2

 

[dickm]

Further instalment from herself.

Returning to the adhesive question - a lot of epoxies are low viscosity, it's one of the problems we have using them for automotive.....

(But I'm guessing that could actually be an advantage here, in getting a uniform coating that would not show through the glass?)

I just noticed that you can get a "glass surface conditioner" by Perm Enamel at craft shops and although the MSDS for the active ingredient says "proprietary bonding agent" I'm pretty sure it will be an organosilane so could be used to improve epoxy adhesive bonding (or urethane) to glass. In fact I think I could justify buying some for work and analysing it in case we need an emergency primer that you can buy anywhere!

No idea if this helps, but...!

 

[Benchwayze]

I would have thought that a 'reversible' adhesive was the way to go. Much less trouble if a pane gets broken. Or have I got the wrong end of the stick again?