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by Larry Maras.
First, let me say that if you want to build a 200 gallon acrylic display tank, this is probably not the place to learn techniques. However, if you want to build a sump, a trickle filter, or several other relatively easy projects that don't require professional quality (but need to hold water) than maybe I can help you out with some of the basics.
What you need:
A basic knowledge of working with wood is helpul, since a lot of the techniques used are very similar to woodworking. Tolerances don't have to be exact, but very close. The glue used for acrylic does not allow for much of a gap on joints. So, the more precise your cuts are, the better seal you will have on the seams. Which brings us to the next requirement.
Tools needed:
For starters, of course a measuring tape and some kind of square. A smaller combination square works well. In order to cut acrylic which is 1/4" thick or more, the best tool that I have found is a table saw. I realize that not everyone owns a table saw, but if you can get access to one through friends or a local school, do so. It will make your projects easier to construct and the quality will be better. I know that some use a hand held power saw for cutting pieces of acrylic. To be honest, with a table saw at my disposal, I have never used these tools for cutting plexi. If you have to go this route, make sure the work is well supported and held steady. Any vibrations may cause the acrylic to crack.
Tip: For a long time I bought all my acrylic at Home Depot. Recently, however, I have started to purchase it at a local acrylic shop. The quality of the material is better, and they will let you search through their scrap pile for bargains. A shop like this also carries more thicknesses and colors than you will find at a home center. Look in the yellow pages under "plastics".
The table saw should have a carbide blade like that used for wood crosscutting, with 40 or more teeth. I know some recommend the special acrylic blades with no "set" to the teeth. I have tried these, and I don't like them. If you can make this work for you, fine. Also, you should have a sanding block with medium grit sandpaper, about 150 is good. Finer paper also if you want to really finish some exposed edges. A sharp utility knife is valuable if you want to cut 1/8" plexi. It can be scored and snapped like drywall. A steel straight edge is required if you plan to use this technique. A work platform--like a bench or one of the Black and Decker Workmates is good to have handy. You will need a place to lay out your project and assemble it for gluing. Tip: The top of the work area should be wood, metal, or some other material the glue will not adhere to your project. Do not use paper. The glue will attach it to your work. You will also need masking tape and/or clamps to hold the pieces in place while the glue dries. As for glue, there are a few different kinds that work, I use methylene chloride, available locally in hardware stores as "Plaskolite". Others use various types of Weld-On adhesive, some are more viscous than others. Methyne chloride requires a syringe-type applicator as well, since it has the consistency of water. If you want or need to bend the acrylic, you will need either a heat strip designed for this purpose, or what I use, a heat gun used for stripping paint.
Let's get started:
Assuming you have made a plan of the project you want to build, measure out the pieces that need to be cut and start running them through the table saw. Leave as much of the protective film on the workpiece as possible. Be sure to have the guard in place and don't stand behind the blade. If small pieces fracture off during cutting, you do not want to be in their path.
Once the pieces have been cut, move them to the work table for assembly. Set the pieces in place, and either use small pieces of masking tape to hold them in place, or clamps. I have also snugged blocks of wood up against a piece standing on it's edge to hold it until the glue sets up. It doesn't take long. Ones the pieces are in place, take the syringe applicator filled with glue, and touch the needle tip to the joint. Squeeze gently until the liquid starts to ooze out, then run the tip down the joint. The process is a lot like applying caulking. If your pieces are being held together with tape, skip over the taped areas. If you apply adhesive here, it will glue the tape to the acrylic. As you do this, you will see the adhesive being drawn into the joint by capillary action. Do as many seams as you can without moving the work. Tip: Try not to spill any adhesive on other parts of the plexiglass! It will cause a permanent burn on the material! Step back and let it dry for 15-30 minutes, depending on the temperature of your work area. At this point you can re-position the work pieces so that other areas can be glued. BE GENTLE. It is still very easy to pull the pieces apart at this point, the joints won't be fully cured for 24 hours. You also now can go back and remove the tape, then glue the skipped areas. Also, if you think a section of the joint did not receive enough glue, go back over it again. Do not be afraid to go back over a joint or seam several times if necessary. After a while you will get a feel for what a properly glued joint looks like.
Once you have glued all the seams, let it stand for 24 hours before filling with water to check for leaks. If you have leaks, mark the areas with a pencil, dump out the water, dry off the acrylic, and re-apply glue to the area.
Bending:
I have used a torch, brute strength, and a heat gun (paint stripper) in attempting to bend acrylic. By far, the best method is the heat gun. It sells for about $25 at a home center. A torch works, but the problem is getting the heat applied consistently. Too close, the work bubbles. Too far away, it won't bend. As for brute strength; forget it. :)
The first time I did this I made a carefully crafted mold out of wood around which I formed the acrylic after heating, to make a nice large-radius, even bend. Now, unless I am building an aquarium, I just bend it over the edge of my table saw. Mark a pencil line square to the work where the center of the bend will be, hang the stock out over the edge of the table--postioning the line at the edge of the table--and clamp the part that rests on the table. Start heating with the gun, moving it slowly back and forth across the line.
DON'T RUSH THIS PART!! Stay far enough from the acrylic so it doesn't melt or bubble. Try about 3 to 4 inches for starters, move closer if you have to. When the plexi gets soft enough, you will see it start to sag. Good--keep heating slowly.
I don't find it necessary to heat both sides of the bend, just the outside. Gently start bending the plexi downward, NOT FORCING IT. Here is where it helps to have two people--one to hold the gun, one to form the bend. When you have bent it to a 90 degree (or whatever) angle, remove the heat from the bend and hold it in place. Here's where making a form out of wood before hand gives you a little more accuracy in the angle. I have found that with a little practice, you can come close enough eye-balling it
Tip: While holding it until the plexi cures, you can also either direct a fan on the bend to speed up the cooling, or drip a small amount of water over it. Your bend is complete.
Drilling:
The best advice I can give is to go slow. Acrylic is easy to drill, but when the bit breaks through the other side it has a tendency to split and crack the material around the hole if too much pressure is being applied. Brand new, sharp bits are especially bad for this. Let the drill cut through at it's own rate. For large holes, buy a good hole saw. It also helps here to put a wood backer under the acrylic. When the hole saw breaks through, it will not fracture as bad. Once you have drilled the hole, you may see that some excess material has melted and formed a ridge around the edge of the hold. Believe me, IT IS HOT! Let it cool for a few seconds and then break it off or scrape it off with a utility knife.
Finishing:
Any exposed edges, like those around the top of a sump, can be pretty sharp. It is a good idea to go over them with the 150 grit sandpaper, rounding the edges so you won't cut yourself later when working inside the sump. If you have an edge that you want to look good, after using the 150 grit paper, go to a 220 or finer to get a smooth surface. Some also use a "flame" technique to get a truly polished look. Tip: Don't sand any edges that will be glued. As in woodworking, an edge right off the saw is more true and square than it will be when you get done sanding it. Some people like to leave the stock extending past the joint, then go back after the joint has fully cured (24 hours) and trim the excess off with a router and a flush trimming bit, like the type used in trimming laminate (Formica).
Sealing the joints:
I don't use a silicone caulk to seal any joints. For one thing, it makes it tough to go back and repair a leak; the joint is buried under the silicone. Also, silicone does not stick very well to acrylic. While it may fill some gaps a bit, it doesn't have any strength when it comes to actually bonding pieces together. My advice would be to just rely on the acrylic glue, and go over the joints until they are leak-proof. But, if you insist on using silicone, use a grade that is safe for aquarium use and let it cure for at least 24 hours before putting the project into your tank.
Leaks:
So, you have built your sump or other container that needs to hold water, you filled it up outside or in the garage (did I mention not to do this in the house?) and IT LEAKS. Don't despair--just empty and dry as described above, and go back over the leaking area, many times if necessary. If your cut wasn't perfect and there is a small gap, position the project so when glue is applied to the gap, it will pool there. Even a short time is enough for the capillary action to take place. If the gap is a little wider, you can make the glue thicker by mixing it with shavings of the plexi. It also helps to apply glue from two sides, if possible. For example, with a right angle joint, apply glue on the inside of the joint, let it set up for a while, then flip it around and apply glue to the back of the joint. Let the repaired area dry, then test again.
Well, your project is completed and you're proud as punch of the money you saved, and what you've created. Good for you. Working with acrylic is not that tough, as you now know, and you should be proud of what you've done. So what's next, that 200 gallon display tank? :) Powered by AkoComment! |
