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WARNING: acrylic glues are dangerous, toxic materials. Always work in a well ventilated area, do not breath the fumes and avoid skin contanct.

Preparing Surfaces

A good surface is important to getting a good bond between the pieces of acrylic. The most important factor is the fit, how closely the two pieces fit together. In the case of straight pieces, both surfaces where they are to be joined need to be flat. So sanding with something like 240 sandpaper stuck down to a flat surface itself with double sided tape works well. Some people recommend going finer than that, but I have found this to be more than sufficient for my needs. Check that both pieces fit together flush and sand as required.

Next important factor is how clean the surfaces are, any particles (sand from the sandpaper) and contaminants (such as oil from the hands) will interfer with the bond. To clean the surfaces use isopropyl alcohol (isopropanol) to wipe them. You can typically find it most easily at a pharmacy/chemist, something like the below image.

Isopropyl alcohol, good for cleaning acrylic surface before gluing.

Once that is all sorted then on to the gluing.

Flush Joints

For perfect, tight joints, the water thin glues do a very good job. WeldOn 3 is one of these glues and is shown in the image below. Ensure that there is some space between the pieces being glued together, using a pin or very thin wire to maintain the gap (the metal wire out of sandwich bag tie is perfect). Then apply the glue using a syringe, allowing for good flow and directional control, which will run into the joint very easily. And fully plastic syringe is best, those with a rubber plunger will degrade/swell over time. Allow it to sit for about 30-60 seconds, until you start to see it disappearing, almost into the joint. Then remove the wires and compress the joint with weight. Allow to dry for a hour or more. Some glue will be expelled from the joint, that is what you are aiming for, but not too much.

WeldOn 3, a water thin acrylic glue.

Imperfect Joints

For joints that have some spacing between them, with a less than perfect fitting, the thicker glues work better. WeldOn 16 is one of these, as is Acryfix 192 and both work well. The provide some filling of the space between the joints, but not a huge amount. Apply the glue to one surface and put the joint together. Allow to sit for 120 seconds or so, allowing it to work on the acrylic, then apply weight to the joint. Allow to dry.

WeldOn 16, a thick acrylic glue.

Acryfix 192, a thick acrylic glue.

If you are exceptionally bad with the spacing between the pieces, or you need something to actually fill in a hole, then the two part WeldOn 40 will do the job. This actually reacts to form acrylic with only a little bit of shrinkage. It is shown in the image below.

Joining Acrylic With Other Materials

If you are trying to glue acrylic to other materials then in most cases an acrylic glue will not work correctly. For acrylic to PVC, you can get some partial bonding using a PVC cement (shown in the image below), but I would only recommend that in locations where a leak would not be a problem and there is a tight fit between the two pieces. Additionally, it is preferential to use the clear cement as this actually forms a bond, where as the blue cement doesn't.

PVC cement or solvent, can provide some weak bonding between acrylic and PVC.

In more critical situations the best glue to use is WeldOn 40. As noted above it reacts to form acrylic, but will also bond between the existing acrylic and PVC. Depending a bit on temperature and the exact ratio of components used, it can take about 30 minutes before it hardens. It is best left for 24 hours to fully cure before doing anything too major to the pieces.

WeldOn 40, a two part acrylic glue that will also bond to PVC.

And the case a lot of people want to do, glass to acrylic. Silicone will make a weak bond to acrylic, so it can be used for things like baffles or weirs. But in the case of where there is substantial pressure on the joint and a leak would be a problem, then it is not suitable. A glue that does a good job at bonding is Bostik Titan Bond Plus, shown in the image below. I cannot say how well it does in pressure situations, but in the cases in which I have used it, its performance is superior to using silicone.

Bostik Titan Bond Plus, epoxy glue that will bond acrylic to glass.

 IPS has a selection guide that can be used to determine the best adhesive to use.

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