Gluing in our context includes solvent-bonding as well as the use of various adhesives. (Joining of other plastics such as HDPE, Polypropylene and uPVC usually involves hot-air welding rather than the use of adhesives.)
Most of the fabrications carried out in our workshop use either cast or extruded acrylic. Depending on the type of article being made, various techniques and adhesives are used. The most basic fabrication would be solvent-bonding of cut panels to create items such as boxes and the like.
More involved fabrication would include the use of Magmabond C2 (2-part adhesive) where joint strength and appearance are prioritized. This step by step photo series shows the repair of an acrylic table (not originally fabricated by us) for a client.
Depending on the desired result, the correct cutting and preparation methods contribute to the quality of the end result. Clear materials are totally unforgiving and errors are often irrecoverable – time and material wasted!
Here, we show the use of Magmabond C2 – preparing the surfaces, masking, cleaning and finally joining… This is followed by grinding and polishing to acquire the perfect transparent result.
The team was very happy with the result until …. the table was bumped during collection…. aaaaand …..
Start over…..
Luckily Ismael is very patient, kind and forgiving towards the difficult nature of working with this stuff!
Solvent bonding
Successful bonding using the likes of methylene chloride, chloroform or MEK relies on material compatibility and good preparation of the join interface surfaces – the smoother the better. In general, it is essential to work in well-ventilated spaces as the constant exposure to fumes from solvents that evaporate as rapidly as these is not ideal – masks and eye protection are strongly recommended as is the use of gloves to protect from excessive exposure to direct contact with the solvents.
Unlike gluing items to each other where the glue might be applied and the faces to be joined then brought together, solvent bonding is most often performed by first positioning the pieces to be joined and then using either a syringe or applicator bottle to introduce the solvent into the join area – the solvent flows into the join by capillary action, attacks the surfaces and results in adhesion of the compatible surfaces. Excess solvent evaporates away leaving a clean, dry join in a short time frame. Light pressure for a few minutes will assist in improved join strength, however, too much pressure will squeeze out the wet solvent and, when released, allow air to enter the join interface making it unsightly as well as weaker. The smoother the surfaces to be joined, the better the potential quality and appearance of the join. Even the most experienced hands will not always achieve perfect joins!
Solvents Containing Filler
Certain adhesives such as Magmabond C1 are solvent-based with acrylic in solution that assist in improving join strength and, once the solvent evaporates, the filler is left in the join interface. The difficult aspect of this join method is the residue of the filler has to be cleaned off from the join area which may require trimming and polishing depending on the application and finish required. It is quite difficult to remove residual material and can result in unsightly joins. This method is often better for opal or colour materials rather than clear – an example would be reinforcing fabricated letters in signage applications.
For high strength, bubble-free joins, Magmabond C2 (2 part adhesive) or similar can be used where required. The methodology around this adhesive is rather different to the solvent-based options both in preparation and execution. The syrup-like consistency of the adhesive often results in extra glue having to be removed once curing is complete. Depending on the type of fabrication and the finish required (eg display or just functional) the removal of the excess might require certain post-gluing operations including trimming, smoothing, buffing, etc to achieve the desired result. Once again, even though this is not a dark art known only to alchemists and other special beings, it does require a step-by-step approach to get it right first time, every time! As with all fabrication, proper planning and sequencing is essential. The working window with these types of adhesive is usually around 10 to 20 minutes, part of which is often taken up by initial standing time to allow air bubbles to rise out of the adhesive before use – this to prevent the introduction of air bubbles into the join interface when introducing the glue.
Final Note of Advice
The most practical approach to all gluing is to learn either by instruction or reading the relevant literature and then experimenting to develop one’s own techniques and skills – if at all possible, working alongside an experienced person and being guided by them in hands-on applications will yield the best future potential.