Darryl Keil Last Activity 2024-10-10 3:42 PM
6 replies, 4615 viewings
 
back
Navigate threads:
< Previous Thread :: Next Thread >
 
^ Top
Michael O. Moore

Posts: 6

Joined: 2014-12-05
Location: Merrimac, MA

User Profile 
Subject : Unibond 800 and Winter Heating
Posted : 2017-03-19 8:09 AM
Post #37583
I suspect my latest two tabletop glue ups with Unibond 800 were bitten by temperature woes. I’m looking for more details on how you’ve all used Rugbuddy type heaters in winter.

In the latest glue up, the top side of my table top was on the bottom of the sandwich in the press and came out with wrinkles (the backer veneer side was facing up in the bag did not wrinkle)… it had a 1mil plastic sheet against the veneer, then a 1/16 natural gum rubber sheet, then the caul etc. I had the rug buddy on the top of the veneer bag. I did a 15 to 1 mix of the Unibond 800.

I’ve done these before without issues. This problem is new to me— But, it was a cold, windy day and I did not preheat the bag (as I’ve since read about here) and the shop temperature was hovering around 70 at the start of the glue up but dipped later (glued at end of day).

How do you all set up your lay up when using a heating blanket like Rugbuddy… which side of Rugbuddy faces down (non-foil, yes?) any new ideas on the top being warmer than the bottom layer? How about putting Rugbuddy underneath the bag instead of on top with packing blankets on top? Looking forward to your experiences, ideas and tips. Thanks.


 
^ Top
Earl

Posts: 75

Joined: 2003-12-04
Location: Pensacola FL

User Profile 
Subject : RE: Unibond 800 and Winter Heating
Posted : 2017-03-20 12:11 PM
Post #37584 - In reply to #37583
70 degrees is not that cold. It seems you may have an application issue. If you have a Rug Buddy it's always a good idea to first heat the platen before inserting the panel. Are you using cauls on top and bottom of your panel? I use 1/4" melamine or white vinyl board cut 1/2" oversize of the panel. That leaves 1/4" overhang. I can't tell you why, other than I always apply glue to the face side last, but my faces are always up. Just a habit I developed.

I've had great success with my Speed Heat rug Buddy. I have to be careful in the summer I've gotten over 117 degrees under the pads. You are covering the heater with pads, correct? I use a small temp gauge to try and make sure I get the panel hot enough without overheating. I like 90-100 degrees. That allows 1-2 hrs press time.

I never use rubber unless absolutely neccessary. I just did a top with shop Sawn veneer using only 1/4" mdf vinyl coated cauls with 100% success.

Study your panel and the problem and pin down your problem. Much easier for you to do it than someone behind a keyboard and not there in person.


 
^ Top
Don Stephan

Posts: 825

Joined: 2003-07-18
Location: Cincinnati, Ohio

User Profile 
Subject : RE: Unibond 800 and Winter Heating
Posted : 2017-03-20 6:50 PM
Post #37585 - In reply to #37583
I'll be making some pressings next week or so here in Cincinnati. Normal studio temp is 66 when I'm working and 60 when I'm home, but when pressing I'll set the thermostat to 70 the night before and leave it at that temp until the morning after the last pressing.

With the platen and bottom caul in the bag I'll lay in place a heating blanket the night before, and turn on as soon as I arrive on pressing days. The bottom caul then will be a few degrees above 70 by the time I put the pressing into the bag.

Don't know if the tip came from Darryl Keil or Paul Schurch, but it is extremely valuable. After getting all in the bag, and the vacuum pump and electric blanket on, pour a little excess glue mix into a small zip lock bag, place in another zip lock bag for good measure, then place on top of the bag and under the electric blanket. When the glue in the zip lock bag is semi-firm it's probably safe to turn off the electric blanket and vacuum pump.


 
^ Top
Michael O. Moore

Posts: 6

Joined: 2014-12-05
Location: Merrimac, MA

User Profile 
Subject : RE: Unibond 800 and Winter Heating
Posted : 2017-03-21 7:54 AM
Post #37586 - In reply to #37585
Thanks for your replies… for the next try I am definitely going to preheat the platen, cauls and bag. I think I will also get a thermometer to see what’s going on.

Don, I do use Darryl’s zip lock bag with adhesive in it trick. And with the last glue-up I noticed a couple hours in that it wasn’t as rubbery as I’d expect. It did remain in the press overnight. Since I’d already done two large tops that go with this I know it’s not the glue itself.

The only difference from the two previous sections that had no problems is that this part of the top includes an inlaid chessboard with banding that includes an end-grain feature in the middle (runs around the squares) and which is just slightly proud of the rest. Earl, that’s why I used the 1/16 rubber as Darryl’s has advised for this kind of issue (I know Paul Schurch uses heavy canvas). The wrinkling was not concentrated just around the banding though.




 
^ Top
Don Stephan

Posts: 825

Joined: 2003-07-18
Location: Cincinnati, Ohio

User Profile 
Subject : RE: Unibond 800 and Winter Heating
Posted : 2017-03-21 8:27 AM
Post #37587 - In reply to #37586
"End grain" immediately caught my eye. When working with solid wood, end grain is expected to make a poor glue joint. A destructive test pressing with this combination of veneer grain directions might be worthwhile.

Did the zip lock bag of veneer adhesive completely harden by the next morning when the pressing was removed from the bag? The answer to that question might help zero in on the cause of the failure.

If during initial vacuum the bag "grabs" the edges of the sandwich first, it might create a tight seal and never create full vacuum over the top caul and pressing. Could this have happened?

When you look at the wrinkled areas, is it possible the veneer expanded a lot here, but was trapped by the surrounding areas, so that it could not lie flat? This would be similar in concept to crotch and some other veneers that have to be flattened first.

Also, please lift some of the veneer at the wrinkling and describe what you find. Is the back of the veneer free of glue? Is the glue still somewhat flexible, suggesting the glue never cured?


 
^ Top
Michael O. Moore

Posts: 6

Joined: 2014-12-05
Location: Merrimac, MA

User Profile 
Subject : RE: Unibond 800 and Winter Heating
Posted : 2017-03-21 9:08 AM
Post #37588 - In reply to #37587
Don, glue dried hard. Excavated several wrinkles, adhesive hard underneath. Glue in bag and mixing pot was also hard next day.

Engrain in narrow, Federal-style banding tried and true in furniture, but hard to slice as thinly as veneer (got it to about 1/32). Made in traditional way. Will also watch for press "edge-grabbing" and will see how next one goes.


 
^ Top
Earl

Posts: 75

Joined: 2003-12-04
Location: Pensacola FL

User Profile 
Subject : RE: Unibond 800 and Winter Heating
Posted : 2017-03-21 9:32 AM
Post #37589 - In reply to #37588
I think Don is on to something. If the banding is surrounding the wrinkled parts, then maybe your rubber was too firm to compress properly and put pressure on those areas. Take a small board 3/4" x 3/4" and see if it compresses rubber by hand. Did you say you had a caul on the bottom?

If the area that did not glueup correctly is not too large it is possible to salvage and replace that area. I've done it before when doing compound curves with too stiff of a veneer.
back
Navigate threads:
< Previous Thread :: Next Thread >
Legend      Notification  
Administrator
Forum Moderator
Registered User
Unregistered User
 Toggle e-mail notification


Logo by MAZY
Running MegaBBS ASP Forum Software v1.5.14b public beta