Weld-on questions

[Brian Robison]

Hi folks,
What's the difference between the Weld-on 4 and the Weld-on 3 ?

[Joe Pelonio]

Both are water-thin. The difference is in drying time, 3 is very fast setting,
4 gives you a little more time to adjust the materials before it sets.

[Mike Null]

Brian
If you haven't used this before there are some things to be careful of.

1. this solvent is sensitive to humidity--the dryer the air the better
2. use plenty, don't starve the joint
3. be sure you have cleaned the areas to be joined, I use DNA
4. one of the surfaces should be roughed to a sandpaper type finish.

[Brian Robison]

Thanks Mike and Joe.
I think I'll get a little of each and do some testing.
I think I'd better do my gluing upstairs, my basement, er laser building has pretty high humidity.

[Mike Null]

Brian

I would try 4 first as there isn't a lot of time difference.

It will evaporate before your eyes and it is nasty stuff--a carcinogen I believe. But it works beautifully.

[Russ Miller]

Here is a link to the manufacturer's website:
http://www.ipscorp.com/industrial/acrylics.html

Weld-On 4 is more difficult to acquire now that it can no longer be shipped via UPS. The had to change some of the solvents used in it and it became a double hazardous material according to UPS. The main ingredient in Acrylic Solvent Cements is Methylene Chloride. At TAP Plastics, we use Weld-On 3 for most applications involving gluing acrylic together.

[Mike Null]

Russ

Would you mind sharing your technique for using this material and any secrets you can pass along. My custom cut plastics supplier passed along the info I posted but to be honest I can only glue without bubbles about 50% of the time.

[Patrick Grady]

I have used Weld-On #3 for years and it is terrific stuff. Joins best when the surfaces are a polished fit with no gaps (it is not a glue/adhesive, it is a contact melt). Use a needle syringe and quickly wet a microstream along the joint, allowing the joint siphon in the solvent, and maintain steady pressure for 5 mins then let sit for a few hours. Make your own long metal needle to avoid drawing solvent into the syringe and that way you can use a plastic disposable syringe repeatedly (syringes made of glass parts are good for this,). You don't need to apply any syringe pressure over short joints, just lay the needle along the joint and allow the edge to draw up the solvent. A glass microtube is great to simple joints, just dip into the can and put finger over the top of the tube and lay it on the joint and quickly 'stream' it along the edge. Weld-On #3 vaporizes out of the can over a few weeks in my shop which is not air-conditioned. I also like to use Weld-On #16 which is a cement (similar to clear model cement) paste which is very slow and hardens in 24 hours. Instructions advise to prep sand joint with 80 grit. Weld-On #3 is tricky and takes practice ; quickly syringe along the joint (avoiding any excess which will leave a 'water mark' ) and at same instant roll and press the joint to void air bubbles. It is better to start with a perfect machined/polished joint edges. By hand, I run the acrylic edge over fine grit sand sheet backed by flat surface while holding the edge at steady angle. Curves are tedious and double sided sand paper helps. Flat lap joints are easy because you start with polished clean surfaces, but bubbles are a problem, so limit the joint surface to minimum and try to rig an instant mechanical press.

[Nancy Laird]

I had a bunch of acrylic pieces to glue up, and could not find Weld-3 anywhere in town. At the local True Value, I found a product called SureHold Plastic Surgery which worked like a charm. Apply a dot, put the two pieces together, hold for about 5-10 seconds, and voila!! you're done.

By the way, it was $2.49 a tube, I glued up 17 clocks with 3-4-5 pieces each, and didn't use even half a tube.

Nancy

[Mike Null]

Nancy

I don't know if you assemble acrylic awards or not but the advantage of Weld-on is that it is an acrylic solvent and cements by melting the two surfaces together. Properly done it is invisible yet the joint is crystal clear.

Do you think the cement you mentioned will do that?

[Nancy Laird]

Mike, except for the places where I blew on it, it's crystal clear. Got a little moisture in a couple of places--hardly noticable.

Nancy

[Mike Null]

Nancy

Does crystal clear mean invisible?

[Nancy Laird]

Nancy

Does crystal clear mean invisible?

Mike,

I pulled out two of the pieces - a clear acrylic and one amber. On the clear (which happened to be one of the ones that I blew on), you can see a little bit of "frosting" where the glue is. On the amber, David had to turn it and squint a little to see just an edge of a glue spot.

That may not be what you are looking for, but for my purposes, it works.

Nancy