Assembly techniques for consideration when using adhesives –
Regardless of the adhesive chosen there are some basic steps in project design, part preparation, and adhesive application and cure to insure a long lived project.
Overview – Adhesives are another tool available to help make the assembly of materials easier. However, to get the maximum benefit from their use you must play to their strengths. For the following discussion the adhesive is assumed to be OK.
The adhesive is only as good as what it is stuck to. Surface cleanliness is a must.
Make sure you have a simple test to insure the adhesive is working properly
Make sure the components are the same each time – substituting materials or a change in supplier needs to be re-evaluated - do not assume they are the same.
Hand fixturing induces lots of variability in the ultimate performance - simple fixturing and clamping will eliminate a major variation in performance.
Once the adhesive has been applied, the parts assembled and fixtured don’t handle or try to readjust things – most adhesives, regardless of how quick they set (with the exception of uv cure materials) continue to develop strength for several days – this includes super glues, 5 minute epoxies, etc. Make sure you do not compromise performance if you need to handle parts soon after assembly.
Suggested accelerated testing to determine suitability of adhesive.
The ultimate responsibility for choosing the right adhesive is the user’s responsibility – take the time to define your expectations and do the testing.
Once you have chosen an adhesive and established a controlled assembly process you need to make sure the result meets your expectation.
If the design will see shock and vibration a quick test may be to drop it on the floor, or throw it down a set of stairs.
If the part is used both indoors and outdoors as well as shock loading you might put the assembly in the freezer and drop it on the floor when cold and then cycle it in a warm environment and drop it.
A dishwasher test is also a good idea as it will give you a sense of moisture resistance and possible discoloration/clouding of the bond line if clarity is important.
Many adhesives will begin to discolor with aging – if clarity is an issue makes sure you investigate this.
A shipping test is also a good idea.
If you encounter a failure during your testing this does not necessarily mean that you have chosen the wrong adhesive – see the tutorial on failure analysis for additional help.
Remember if the adhesive worked part of the time it is not the adhesive that is the problem.
There are three types of failure – cohesive, adhesive and substrate failure.
Cohesive failure is when the adhesive fails within itself – there is usually adhesive on both mating parts – if this occurs it normally means that either the adhesive hasn’t been cured properly or the adhesive isn’t strong enough for the application. If the product has worked in the past then the most probable reason is that the adhesive wasn’t cured properly.
Adhesive failure means that the adhesive has stayed with one of the parts and the other surface is clean/no adhesive residue. There is any number of reasons that could explain this - cleanliness, weak surface oxide layer, plating variation, etc.
Substrate failure – one of the two parts being joined fractures and fails. Sometimes this is good, sometimes it is bad. In the case of brittle materials such as glass it might not be desirable.
It is recommended that you talk with the supplier of adhesive if failure occurs -
Mounting Hardware to mirrors and Opaque Glass
The following procedure applies to the use of AP 021 family of adhesives when used with the activator AP 020.
Clean glass and hardware/signage with isopropyl alcohol.
Additional strength can be achieved by light abrasion to hardware or signage prior to cleaning.
Application of the Activator AP 020
Brush a light film of activator on the glass. – allow activator to dry.
Important - Recap the activator bottle as the material will deteriorate over time once exposed to air.
Apply a small amount of adhesive in drop form to the center of the piece of hardware or a series of small dots if working with light gage metal letters or foils.
Press the hardware to the glass to spread the adhesive so that it scrubs the activated surface.
Important: Do not spreads the adhesive on the hardware – insure that mating the hardware or signage .
Press and hold the hardware against the glass for approximately 45 seconds to achieve a hard fixture. Adhesive will continue to develop strength rapidly and full cure will occur in 24 hours at room temperature (70 degrees F). See tutorial on how to establish fixture with activator AP 020.
Important: Do not move the parts relative to one another until a hard fixture occurs.
Occasionally, adhesive will squeeze out of the glue joint when assembled - after curing, the squeeze out can have a tacky feel to it - this is not unusual.
Squeeze out can be cleaned up by cutting away the material with a razor knife and using isopropyl alcohol to remove the balance of the residue.
Adhesives for Attachment of foiled back crystals
Suggested gluing recommendations to achieve long lived attachment of foiled back crystal such as Swarovski flat backs and chatons to glass, metal findings, and other materials.
Attachment to rigid non flexible surfaces such as metal and glass:
If you have line of sight to the glue line through a transparent surface such as glass then a light activated adhesive such as AP 012 (self leveling grade) or the AP 012 Gel (non migrating) which can be fixed in seconds with low intensity, UV-A backlight.
Regardless of adhesive chosen, both the foil back and surface to which the crystal is being attached must be clean – the recommended cleaner is isopropyl alcohol.
If the rigid surface does not allow light to get to the glue line then a two step adhesive is required such as AP 021 and activator AP 020. Fixture time for handling purposes with this approach is normally less than 30 seconds. See tutorial on how to use this adhesive and activator combination.
For flexible surfaces such as flip flops, leather, flexible vinyl, or cloth, special care must be taken to insure long lived bonds. Cyanoacrylates and solvent based contact cement can be used for attachment of crystals with proper surface preparation.
Mosaic construction with Light curing adhesives
Elements that make up the actual mosaics can be made from any type of media – metal foils, ceramics, stained glass, art glass, etc. – backing for these designs/art forms vary as well. This tutorial deals with the attachment of the mosaic elements to either clear glass or clear plastic.
Light curing adhesives are ideally suited for fabricating many types of mosaics because of the on demand curing feature. Adhesive is applied to either the mosaic piece or the backing plate, positioned and checked for appearance and then exposed to low intensity UV-A light for a very brief time to fully cure the adhesive. Nothing happens until you are ready to make it happen - on demand.
Adhesive selection is fairly straight forward once you have defined the media and its backing, the size of the elements to be mounted on the backing, and the environment in which you plan to use the mosaic once it has been built.
For interior applications that are not part of a bath/pool/or high humidity environment where condensate readily form the recommended product family is AP 012 – regardless of whether the backing is plastic or glass. For applications that can be exposed to high humidity, changes in temperature (freeze/thaw), or where extended life (years) is desired …a glass backing , a pretreatment with the silane surface prep (Gap-4) is recommended or ”Ask Chuck “.. All adhesive bonds are subjected to aging. The life of the bond is dependent on a number of variables (see tutorial). The fabricator is responsible for the ultimate decision as to product selection.
Tips for creating bubble free films
Whenever possible work with adhesives that are “Newtonian” in nature – i.e. they get thinner when warmed up.
A warm surface lets the adhesive wet out better and helps release any air that may be entrained in the adhesive.
Make sure the surface is clean - take the time to clean it with an isopropyl alcohol wipe.
Apply adhesive slowly and centrally on the surface and allow the adhesive to self level
Inspect the film of adhesive after it has had a chance to self level for air bubbles – remove using a clean, sharp pin - they will either break free or you can drag them out to the edge of the film where they will break.
Do not lay the mating part directly on the film - for larger laminates create a teardrop pattern of adhesive that extends to one edge (sort of like a balloon with a sting attached).
Position the mating part at the end of the “string” of adhesive, perpendicular to it and slowly lower the surface into the film – do not allow the surface of the part to drop into the adhesive – imagine that the surface is hinged to the edge of the string of adhesive and you are slowly closing a door.
Take your time with the previous step – do not force the film to spread once the surfaces are mated – allow them to stabilize – if the film does not completely spread across the surfaces – a small additional weight can be added to facilitate spread – do not push the surface into the film of adhesive.
When the adhesive weeps out of the parting line between the two parts and you are satisfied that no bubbles are present in the film expose the assembly to a low intensity uv light source – make sure the full surface is exposed at once – do not try and tack the parts and move the light around.
If you are working with a mixed system rather than a single component uv cure material you will put air in the system when you are mixing it – there several techniques to remove air – you can degas the material once mixed and follow the procedure above or you can allow the adhesive to self level and then use a shop torch to kiss the surface of the adhesive film to cause air to rise and break out of the film. IF the mixed adhesive is very thin it may degas by itself – check the working/open time that the mixed system gives you – the longer the better in terms of an air free film.
Tutorial – High Clarity UV Adhesives for Garden Art
Garden art is best described as turning miscellaneous pieces of glass, ceramic, wine bottles, pressed glass, sea glass and metal into an indoor or outdoor sculpture. The real challenge is in building the sculpture with different pieces that were never designed to go together in the first place – the AP 011 family is recommended as a good starting point.
Repair of crystal components with high clarity, light curing adhesives
Directions for use – (Suggested)
First Step is to determine fixture and cure using the available UV light source – there is a wide variety of UV lights that are used for aquariums, CSI work, grow lights, inspection of money, scorpion hunting, die penetrant inspection, etc. – all will work, including bright sunlight. The key is using a light that emits energy in the 350-410 nm spectrum.
Recommended repair procedure:
Remove old adhesive from surfaces and wipe with isopropyl alcohol.
Using non hardening clay create a bed that one of the pieces can be mounted in.
Dispense a drop of adhesive into a dish.
Using a toothpick, wet the end of it in the adhesive and touch it off (transfer it) onto the crystal embedded in the clay support.
Assemble the remaining piece using only enough pressure to uniformly spread the adhesive.
For hand held parts have another person bring the UV source into position to fixture and cure the glue line – do not try to move or adjust parts as you will compromise repair.
Expose the repair at a fixed distance from the UV light source until fixture is achieved.
Continue to hold the light source on the glue line for a multiple of (5) times the amount of time it took you to achieve fixture.
Understanding fixture and full cure with the available light source.
Set the light at a fixed distance from the glue line – typically not more than 3-4” with low intensity lights.
Apply a drop of adhesive to a piece of glass and place another small piece of glass (microscope glass slides are ideal) on the drop of adhesive and press the two pieces of glass together with light finger pressure to spread the adhesive.
Place the glass pieces under the UV light source at a fixed distance from the source and slowly scissor the pieces until they set – the time it takes for this to occur is considered fixture time – it is not full cure. An alternate method is to place the glass under the source and check it after 5 second intervals – fixture will occur with most low energy sources in 5 to 30 seconds.
Full cure will typically require that you leave the parts exposed to the light source for a multiple of (5) times the fixture (5 second fixture times 5 equals 25 seconds minimum – longer is better).
Important – the adhesive will not continue to cure if the light source is removed before the total cure time is reached.
Do’s and don’ts revisited – unasked questions answered
Don't look directly at the UV light source - wear UV blocking eye protection.
Don't adjust/move/wiggle the repair when the light is trying to fixture/cure the adhesive.
The product will not continue to cure if you take the light away - honor the multiple of (5) times fixture. Longer dwell time is OK .
Keep the light at the same distance from the glue line - closer is better as intensity varies inversely with the distance from the glue line.
Your fingers will transmit oil to the surface of the crystal - don't touch the area you plan to apply the glue to after you have cleaned it – isopropyl alcohol wipes are recommended.
The adhesive is classified as a mild skin sensitizer and eye irritant - use it in a well ventilated area and wear throw away nitrile gloves.
To dispose of the unused/excess adhesive dispense it into a zip lock bag and lay it out in the sun for an hour or so - the cured adhesive and empty syringe are considered plastic for disposal purposes.
Product left in the syringe pack will not deteriorate when stored at room temperature away from sunlight – packages are date coded and normally are usable for a minimum of one year from date code.
When using low intensity UV florescent black lights or LED UV lights any material that squeezes out of the joint will remain tacky at the surface because of air inhibition (that's what keeps the adhesive a liquid until the UV light hits it). After cure the tacky surface can be cleaned with isopropyl alcohol. A utility knife can be used to clean away extruded adhesive that is cured.
Glass display Case Construction
The use of light curing adhesives can minimize/eliminate the need for polishing and chamfering glass as the glue line will wet out and hide minor surface imperfections – The result is a clear joint with no visible surface imperfections.
Recommended product for mitered and polished fixtured glass is AP 017
Clean surfaces with isopropyl alcohol, fixture glass and apply adhesive AP 017 along the full length of the seam. Material will wick into the joint - AP 017 cures only when exposed to UV-A light. It is recommended that you cure the full seam at the same time rather than spot curing the product. UV-A florescent black lights are recommended for this work. Product is available in 15 gram and 45 gram syringe packs. Typical fixture time is 45 seconds with full cure in 5 minutes. Distance of 40 watt UV-A florescent black light from mitered edge is 2”. Fixture and cure times are representative and fixture and cure for the type of glass must be determined by user – contact Chuck if you need guidance. Refer to tutorial on fixturing.
Approximate coverage for 15 gram pack is 50+ feet for 3/8” polished edge.
Recommended product for mitered, unpolished fixtured glass is also AP 017
For piece by piece construction and repairs of high clarity gel AP 016 is recommended.
Both products can be used to attach hardware to glass - suitability of performance is the responsibility of the user.
Clean up – excess material outside the joint can be cleaned away with a razor and an isopropyl alcohol wipe.