Inspecting clear glass for clarity

[Jon Lipovac]

How are you guys checking your clear glass for clarity before glue up?

I switched from Bearpaw to Gordon because of draw weight issues and I had heard that Gordon’s was getting better with their clarity, but I just laid up some darker limbs and they are disappointing to say the least.

I’ve had some Bearlaw with cloudy spots but not like this.

[Mad Max]

I had some Gordons that had streaks, sanded a 2" area and cleared coated and it was good.
Only surface marks.

[Crooked Stic]

That looks like air bubbles to me. Whatkind of wood?
I usually leave them out for awhile depending on if ther is a chance that the wood needs to gas off

[kennym]

That kind of looks like bubbles like Mike said to me also, most streaks look like a strand or two of glass filament that didn't get wetted enough.

Dale Stahl told me long ago to lay it sanded side up on a black surface and you will see "most" of them. I know some guys wet with alcohol too, but I don't like wiping with a rag or putting anything on glass except compressed air and glue.

I wish there were a 100 % way to make sure before glue up.

[Kirkll]

Typically you can wipe it with acetone and hold it up to the light and see any bad streaks, but you'll never see cloudy spots until it comes out of the form.  I warn all my customers that i do not guarantee glass clarity. If you go with dark veneers under glass, you get what you get.... What i really hate is after the bow has been shot awhile sometimes you get little tiny stress cracks that look terrible. It's not a structural issue, and doesn't effect longevity... But it looks bad.   I use acetone on my glass to remove any oils transferred to the glass by handling it with bare hands right before lay up.

I try and stay with light colored veneers every chance i get, and just warn guys what happens using black walnut , bubinga, or other dark veneers.

With that being said... Those look like air bubbles to me too.... It happens sometimes...  Kirk

[Jon Lipovac]

Thanks for the replies guys.

You've got me convinced that they are air bubbles as well. I do notice that they are clear in the area of the curve. My guess is the sheering motion of the glass when you press into the curve helped push some trapped air out?

Also, I've been using Huntsmans for my glue ups and have been extremely happy with the ease of it all and the consistancy. I typically heat it up to 85* in my hotbox to the viscosity is the same from limb to limb regardless of the time of year. But, I use a thin foam roller with it and I wonder if I'm not inadvertantly pushing small air bubbles into the glue when I'm rolling. Especially if I start to run a little low near the end and try to push epoxy out of the roller. I'll have to keep an eye on that.

If I notice any slight air bubbles or even if I don't see any, I might experiment with running a torch over it real quick and light to pull the air out like i've seen guys do on epoxy table pours.

[Mad Max]

Maybe your not getting enough glue in there.

[Jon Lipovac]

Maybe your not getting enough glue in there.

Yeah, I thought about that but I don't think that is it. There is a decent amount of squezze out under pressure(50psi). I roll it on pretty thick then back roll it to pick up any extra that doesn't need to be there. The veneers are .020 and seem to get completely saturated all the way through.

[Kirkll]

what kind of heat are you using? and how hot are you cooking? it and how long? I cook my clear glass limbs at lower temp, for a bit longer.... i have had issues with too much heat before.

[Jon Lipovac]

what kind of heat are you using? and how hot are you cooking? it and how long? I cook my clear glass limbs at lower temp, for a bit longer.... i have had issues with too much heat before.

3 hrs in an insulated hot box with digital thermostat set for 130-135 so the lights don’t cycle on and off too frequently.

[Kirkll]

Well then heat is not an issue… my problems were associated with heat strips getting 180-200 degrees back when I was experimenting with different heat strip designs.   Just a thought.   Kirk

[Tim Finley]

That is not air bubbles that is in the glass Ive seen this numerous times exactly like that, you will see it with dark veneers .

[Bryan Adolphe]

Hey Jon yeah that’s disappointing when you see that coming through your glass all I know is foam rollers definitely promote air bubbles on any slick surface what I’ve always done is applied it then a quick once over with an applicator or brush takes care of the bubbles, just a thought.

[Kirkll]

I tried that Huntsman epoxy when it was first introduced and everyone was giving it a go…and…  I didn’t care for the thin viscosity at all myself. But then again… I grind my lams with 36 - 40 grit paper on my drum sander. This works fine with the thicker viscosity EA 40 smooth on, but I never felt I had enough coverage with the huntsman. So I tried grinding to 80 grit, and got better spreading results using a putty knife rather than a roller… but… it was a mess being so thin, and didn’t care for grinding with 80 grit paper either… I finally gave up on it and went back to the tried and true EA 40.

Tim…. I believe you are mistaken on this being glass spots. Those are definitely air bubbles.      Kirk

[Mark R]

I tend to agree with Mr. Finley, too many uneven spots to be air bubbles between lams and I've seen this in glass also, but foam rollers can pull the epoxy up from the lams more than desired and also leave some of the foam in the epoxy, better to use a solid wall paper roller to spread evenly. JMHO

[kennym]

Jon, what wood are the lams?

I had some Jatoba do similar but not as many, figured it was just oily. It actually did it in same place on both top and bottom limb...

[Jon Lipovac]

Kenny,

They are padauk, I'm gonna lay up another tonight and pay close attention to see what happens.

[Kirkll]

Kenny,

They are padauk, I'm gonna lay up another tonight and pay close attention to see what happens.

Paduke has pretty deep grain slots. You might have better luck using EA 40