Glues & Adhesives

Rev. 2002-07-05, 2003-08-08, -09-10, -09-24, 2006-06-15, 2007-05-10, -05-25,
2008-04-14, 2009-02-20 (layout), -03-02, 2011-02-19

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Epoxies

UV Bonding
Silicone Bonding
Using E-6000
Using Gorilla Glue
Using Thin vs. Thick
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Coldworking including drilling & cutting glass

 
For all practical purposes, glue is an adhesive and vice versa. There are some people that think a "glue" is weaker, etc., while an "adhesive" is high tech and modern. Either one must be matched to the job and a wonderful glue for metal may simply never stick to plastic and vice versa.  Since this is a glass related website, the adhesives for non-glass stuff will mostly be mentioned in connection with tools or gluing glass to other stuff.
Using the proper materials and with proper preparation, it is possible to glue up a chunk of optical glass from other chunks, where the seams are virtually invisible yet the result is strong enough to be ground smooth and otherwise worked. Since the initial chunks can be (indeed must be) worked to polish the smooth gluing surfaces, they can also be worked to provide inside shapes including leaving holes and surface treatments including etching and dichroic treatment. There are artists who make cities inside glass and others who make spheres and other shapes. 2009-03-02
 
On the other hand, there are several glues that permit adhering glass reliably to other glass and to other materials. The silicone based adhesives are particularly good and E-6000 (Eclectic Products, 800-767-4667) is spoken of often. Uses for these glues include attaching glass to bases made of other materials - marble, granite, and wood - and making up laminates such as the botanical weights of Paul Stankard where dark stone is adhered to the side of the glass portion.
 
Jim Bowman's clock of laminated glass at DART West End StationThere is a whole subcategory of glass sculpture that involves cutting and shaping thick pieces of flat window glass and stacking and gluing them for effect. Jim Bowman has a clock next the the DART Rail West End station in Dallas which has what looks like a tornado descending through the layers of green glass - the tornado was blasted in each piece before assembly. Similar material has been used for art deco like skyscraper models and tables.
The major categories of glues for glass are UV (ultraviolet) curing acrylics, two part epoxy resins, and silicone based RTV rubbers. I am weak on super glues - cyanoacrylates  - which I have not used. http://en.wikipedia.org/wiki/Cyanoacrylate says they are not good with glass and weak in shear or when cold.
The first are typically thin, very clear (water clear) and slow to set until exposed to UV light from sunlight or a special lamp. They are used when very thin glue lines are desired and typically have almost no filling capacity - the materials must fit perfectly. When the glass is opaque or very dark, accelerants are available to cure the epoxy in the way that two part epoxies or fiberglass resin is cured.
 
Can I add a few notes? UV glass bonding adhesives are primarily acrylic based, unlike 2 part epoxies. These days they bond with equal structural strength to typical epoxies, and can be water white and moisture resistant. One recommendation would be Dymax 620 or Dymax 429. They are single part and room temperature curing. In high temperature and solvent resistance, epoxies can be superior, but in other aspects they compare well. These UV curing acrylic chemistries are used for almost all car windshield repairs, by the way.
You would use the same amounts of a UV curing adhesive as an epoxy, as both are gap filling and structural.
You are correct in saying that you can manipulate your parts after applying the adhesive, because no curing starts until the adhesive is exposed to the curing light. This is a reason why UV adhesives are used a lot for lens bonding and fiber optics, where the parts need to be focused or aligned. Uncured adhesive can be easily wiped away with, say, isopropanol. (isopropyl alcohol)
One caution about using sunlight for UV curing - you may not achieve full polymerization with just sunlight as opposed to a UV lamp, and therefore not achieve all the desired physical properties.
Regards,
Peter  [Peter Swanson, Oxfordshire, England, INTERTRONICS [Posted to Rec.crafts.glass 2002-06-27]
 
Hxtal is the most recommended two part brand HXTAL Okay, so what is HXTAL and why is it so great? [This link Adhesive for glass--Conservation DistList is in the middle of a discussion of wicking adhesives and discusses a Loctite product available in hardware stores.] 
A less used part of the category in art work is opaque two-part epoxies. In my experience these are never clear, although some form a clear yellow cream when mixed from a clear and amber parts.  Epoxies intended to be used in smaller quantities have the body ingredient and the accelerator/curing agent bulked out so even lines of each can be laid out from the tubes or connect syringes. The brands 5 Minute and Two Ton epoxies in tubes are like this while PC-7 is a paste where even quantities are dug out. All are mixed to a uniform color.  Those designed to be used in bulk have a tiny bottle of the agent and quart or gallon quantities of the body, with the agent being added in drop or teaspoon quantities to cups and pounds of body.  Fiberglass resin and Bondo are examples of the latter. 2006-06-15 
 
Silicone adhesives include those that are thick and stay pretty soft when set - GE 100% Silicone Caulk & Adhesive - and those that get very stiff when set - E6000 & Goop.  Some of the Goop adhesives flow and some stand up while E6000 is self leveling. All will bridge substantial gaps if they stay in place. 2008-04-14
Silicone based rubber adhesives were first developed by GE and marketed as high temperature Room Temperature Vulcanizing (RTV) rubber. The stuff sold as household adhesive or tub caulk will stand up to 400F and others will go high enough to cast lead in a rubber mold taken flexibly off the original. The GE products, which are still on the market, come in clear, white, grey, beige and black to match decorating schemes. They normally can not be painted. Clear is not water clear, but has the hazy appearance of a few drops of milk in water. Against an opaque background (a tub for example) it takes on the color of the backing.
When applied to glass, it catches the light and is distinctly a different material than the glass. I used it on my test pieces for my whirly gig.

Whirly gig with glass installed, silicone clear sealant being used

It stays rubbery and can be cut through with a wire or razor for removal. I have used it for years for insulating wires, potting electronics, and sealing holes - making my own stoppers as it were. SSR on cable, sealled with siliicon sealant
E-6000 is a silicone adhesive widely used in the arts which is marketed as being extra strong and extra tough and gluing almost anything to almost anything. I have my first tube - unopened - in front of me as I write this (2001-12-16) There is a clear warning on the back about the fumes and about the fact it is not UV tolerant and should be painted if exposed. UV-6800 from the same company should be used when exposed to sunlight and it is apparently grey. [I am told it is clear, but haven't found any.]. EPI
Goop is a closely related product line from the same company.  Each of the half dozen or more products has certain modified characteristics, for example, Marine Goop is more UV resistant and doesn't slump flat as E-6000 does (see below). http://www.amazinggoop.com/ shows the products, but it is frames and takes a ridiculous amount of time to load (many seconds even on DSL.) From an e-mail: "Thank you for inquiring about our Amazing GOOP® Adhesives. To answer your question, here are the differences between the different items in the GOOP Adhesives line. Craft GOOP® contain a thinner formula for precise, detailed work. Amazing Goop®, Wood & Furniture ®, Automotive GOOP®, Household GOOP® and Plumbing GOOP® are all the same formula.  Lawn & Garden GOOP®, Marine GOOP®, RV GOOP® and Sport and Outdoor GOOP® are all UV-resistant.  Shoe GOO® is a more rubbery formula allowing for greater flexibility. If you have additional questions or need further assistance, please let us know at 800-767-4667. Sincerely, Technical Customer Service Eclectic Products, Inc."  2007-05-10
2001-12-22 Opened my tube of E-6000 and glued up some window glass in a test piece. So stinky I shall not use it in the house again and thinner than I expected. It flowed on the glass and puddled. I will test it for strength - I cleaned the pieces with soap and water - and put it outside. Tube says this stuff is self leveling and of medium viscosity - this can be seen in the picture at the bottom corner glue spot and along the diagonal. (click to enlarge) I have put it out to weather and be sun exposed 2001-12-23. [Attempting to clean up cured E-6000, it is much tougher than RTV.] [This test piece was left out in rain and exposed to direct Texas sun for 5-6 hours a day.  On 2003-09-05, it was found fallen apart, with both bottom joints released.]

Three thicknesses of flat glass glued up with E-6000

I made up some curved glass pieces for another whirligig and used E-6000 to glue them to the metal arms. Only as I was using it did I notice that it says that on NON-porous materials it should be applied to both surfaces and let stand for about 10 minutes before pressing together. This is unlike other glues (say Duco) which require pre-coating of porous materials and I had skipped over it mentally before. I assume that some vapor has to escape or some moisture enter to speed setting.
To re-slump the glass, I would have to get it off the arms. My first attempt at burning out the E-6000 by going to 600F failed and left the glue hanging on. A run to 850 burned it out and left the glass free.
When I partially followed the directions - applied a coat to the metal arm, pushed the pieces together, set them apart for about 5 minutes - I found that the behavior was much closer to a contact adhesive - i.e. harder to reposition. So I can choose the adjustability. 2002-06-01

Completed spinner

 

I have begun using Gorilla Glue and am finding it very interesting.  One is supposed to use small amounts and allow for the fact that it foams up, which it certainly does.  Items are to be clamped firmly for 3-4 hours until it sets.   Moisture is required and one surface is to be wet when the glue is applied to the other surface. The glue is a mix of a polymer and isocyanurate (Super Glue) for curing with moisture and converts to a plastic when set.

 I have used it on a cherry steam stick, soaking in water and not yet used and on a pounder for sand casting, gluing on the added width pieces for the blunt end.  I am going to try gluing an oilite bushing into a tube tonight or this weekend. 2003-08-08 
 I have directly glued a wood block to be immersed in water to an aluminum handle and will see how that stands up. 2003-09-10. [Checked on 2008-04-04 after winter -and years- in water and still firm]]  The image shows the completed steam stick, not much exposure of the glue and the dowel and cup of a neck former, the cup being only glued to the aluminum. The oilite bushing gluing work fine for strength I was off on alignment and I am now trying to make the action smooth. 2003-09-24  There are a couple of negatives about Gorilla Glue: It stains hands and clothing and if left the only removal method on skin is time.  The foam (shown in the picture above) is weak and can be cut off easily, but it tries to push the joint apart so joints must be clamped or weighted. When the glue is set, it is a plastic (according to the maker) and is not only waterproof but solvent proof.  Nothing will soften it, which is a terrible problem if used in the wrong place or badly.
Examples of glued wet wood tools
 I was contacted about releasing a broken piano leg on a valuable unit that was repaired with Gorilla Glue, a major no-no -- furniture of value should be repaired with stuff that can be undone, like hide glue.  Queries on the internet suggested freezing it.
  I thought of RF (radio frequency) like microwaves. I made up two test blocks of pine and plywood and let them set for 24 hours.  One is now in my freezer, I don't think it will work. [It didn't, just as strong.]  The other I heated for 30 seconds at a time, checking for wood damage joint failure each time. [This was a joint about 1-1/2" square in pieces about twice that long in a 900 watt oven.]  The wood got quite hot and after about 2-1/2 minutes of heating, I thought I felt the joint give a bit and was able to pry it apart with my hands, protected by a towel, after 30 seconds more.  The center of the joint area showed a brown mark I take to be overheating.  Before affirming that heat will work reliably, I would want to try it on hardwood and on joints that had set longer.  Also, a finished piece might have damage to the finish from the heat. 2007-05-09   I have glued up a pair of oak blocks giving them longer to set/dry.
Back on the 10th of May, I cut short pieces of 1x2" red oak from a very dry piece in my shop, sanded to remove surface grime and glued them with clamping. After overnight in the clamp, I removed it, dated it and kept it in the house until the 24th (14 days) when cleaned off the expanded foam and placed it in the microwave.

 It got very hot very fast and after 49 seconds of a planned 60 second run, I popped the door because of the frying sounds and tried to pry it apart holding with padding. No success. I returned it to the microwave, slightly cooled and gave it 30 seconds more.

It was very, very hot to handle and I was able to take the pieces apart with slight pressure with a dull knife across the corner.  Note the considerable darkening in the area of the glue. The darkest center portion shows wood damage in the form of small cracks across the grain and the wood appears slightly recessed. Glossy glue remains on the wood around this area.

In the earlier test with a pine 1x2 across 1/2" plywood, the dark brown shows the same effect to a lesser degree. The pine was microwaved a couple of days after gluing and the lesser damage may be due to the higher resin content of pine, the probable higher moisture content due in part to dampening to glue and the soft wood holding more water for the shorter setting time, and the fact that the pine was heated in 30 second batches with inspection after each one for a total of about 2:30  2007-05-25


Using Thin versus Thick Glues - Glues/Adhesives come in several consistencies and using them out of their intended process can require special steps and may result in failure.  Among my descriptive choices are water thin, creamy, house glue, toothpaste, and putty
  • water thin - super glue and UV cure are examples of clues that flow into small cracks and/or form a very thin coat on a flat surface.  Very difficult to use if a gap is large because there is no filling ability and will flow out of vertical cracks even if taped (see next)
  • creamy - Elmer's school and wood glues are examples of those which will flow or drip if the surface is other than flat although they tend not to flow out of cracks just open enough to permit sliding in a knife or razor blade. Not necessarily opaque, may be clear as is E-6000 which flows to self-leveling.  Moderate filling ability to bridge across gaps.  A somewhat wide vertical crack will allow flow and can be coped with by placing masking tape across the crack.  Gorilla glue is an exception because it goes on creamy, but foams up to fill cracks, but is supposed to be clamped to keep from pushing the joint open.
  • house glue - this is the clear glue like Duco that I grew up with.  Today some clear glues in small tubes are creamy.  The difference is that house glues do not flow when applied to a tilted surface.  They normally smash down flat and are not very filling.  Epoxy resin for fiberglass usually starts creamy but can be thickened.
  • toothpaste - these glues come out of a tube or be dug out of a container and mixed but each results in something as thick as toothpaste that may be spread flat, but if left in lumps may not flatten easily.  The most common examples are probably the thicker GOOP glues and 100% silicone glues and tub caulks.  Two part epoxies, such as PC-7, may be more like a putty coming out their container but as mixed, they become more like toothpaste.
  • putty - a few glues are very thick, like putty for windows.  These can actually be used for sculpture and usually come with some method for thinning when this thickness is not appropriate.  These are usually two-part epoxy requiring thorough mixing because the thick material does not allow solvents to escape.  Bondo used for car and boat body work and PC-7 are examples.  2006-06-15

SUPER-HIGH TEMP ADHESIVES - Recently I became aware of super high temperature adhesives, some of which can go up to 4000F although most limit above the melting point of glass but below 3000F. High Temperature Adhesives and Epoxies, Ceramics, Insulation, Epoxies and Epoxy 2006-10-06

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