Acrylic Fabrication Q & A

[Turbo's Aquatics]

The issues with Chemcast go way back to when they first came on to the market I believe (that was over 10 years ago). They had several manufacturers using their product, which was much less expensive than other brands, and thus selling a bunch. About 6 months later, all those tanks started literally falling apart at the seams. That of course gave the brand a black eye in the aquarium world.

I'm pretty sure the issue was related to their material composition in combination with the solvent used. Something that a lot of fabricators don't understand is that it's not universal that X solvent or Y method works the same way on all acrylic. That's why most of the reputable manufacturers use either Arkema or Polycast products, because they have a level of consistency over the years. Acrylite used to, and then there was a change in their manufacturing and they got bumped down a bit in favoritism.

I've seen quite a few tanks built more recently using Chemcast and I haven't heard any widespread reports of tanks blowing up. I'd say in general it's OK.

They do not exclusively build aquariums but I could not actually find an acrylic builder in Canada so this was my only option.

This is the only thing that gives me pause, I understand that a fab shop wouldn't be dedicated to building only aquariums, but I'd also want to know what their level of expertise/knowledge is with acrylic aquarium fabrication. It's something that I consider a specialized subset of acrylic fabrication.

 

[Justin_Reef]

The issues with Chemcast go way back to when they first came on to the market I believe (that was over 10 years ago). They had several manufacturers using their product, which was much less expensive than other brands, and thus selling a bunch. About 6 months later, all those tanks started literally falling apart at the seams. That of course gave the brand a black eye in the aquarium world.

I'm pretty sure the issue was related to their material composition in combination with the solvent used. Something that a lot of fabricators don't understand is that it's not universal that X solvent or Y method works the same way on all acrylic. That's why most of the reputable manufacturers use either Arkema or Polycast products, because they have a level of consistency over the years. Acrylite used to, and then there was a change in their manufacturing and they got bumped down a bit in favoritism.

I've seen quite a few tanks built more recently using Chemcast and I haven't heard any widespread reports of tanks blowing up. I'd say in general it's OK.


This is the only thing that gives me pause, I understand that a fab shop wouldn't be dedicated to building only aquariums, but I'd also want to know what their level of expertise/knowledge is with acrylic aquarium fabrication. It's something that I consider a specialized subset of acrylic fabrication.

Hey, thank you so much for the feedback.

So they do build aquariums, sorry I was not very clear on this. They are just not a dedicated aquarium builder. They have worked with a few public aquariums as well. I am not sure to what extent but that made me feel pretty confident in their skillset.

I am really not too sure what to do. I guess at the very least I would take them up on their offer to anneal the tank. I did ask if they would rebuild it in another material but I don't have an answer yet.

 

[Turbo's Aquatics]

If they know what they are doing, i.e. they build aquariums on a regular basis, I wouldn't worry about it. I wouldn't even anneal it. If they have a track record of building tanks and very few failures, if any, no worries.

 

[Justin_Reef]

I ultimately decided to get a refund. I don't think I would ever feel 100% comfortable with 200G of water in a tank made from Chemcast. Thanks for all the help. Now I need to find a new builder. You guys are lucky to have so many options in the US!!

 

[Cabinetman]

I ultimately decided to get a refund. I don't think I would ever feel 100% comfortable with 200G of water in a tank made from Chemcast. Thanks for all the help. Now I need to find a new builder. You guys are lucky to have so many options in the US!!

Where are you located? I’m in Nova Scotia

 

[Justin_Reef]

Where are you located? I’m in Nova Scotia

Hey, I am in Vancouver, BC.

Do you know of any acrylic aquarium builders in Canada? I did reach out to two in Ontario but neither one ever replied to my request.

 

[lapin]

I ultimately decided to get a refund. I don't think I would ever feel 100% comfortable with 200G of water in a tank made from Chemcast. Thanks for all the help. Now I need to find a new builder. You guys are lucky to have so many options in the US!!

I built my 600g tank out of Chemncast GP. Its going on 3 years old. Post is a bit late but just for future reference.

 

[Soup Sandwich]

Hello all,

I was hoping to get some input on the attached pictures. The tank is 60x24x24. Half inch thick acrylic with 4” brace around the entire top perimeter and a 6” brace down the center.
I have a concern about the 3 attached pictures. They are areas in the seam that came out less than perfect. Two of them are on the bottom, while one is on the sides at about halfway up the tank

 

[Turbo's Aquatics]

The first pic: the bottom panel is rough sawn on the edge, telling me that it is cut to the exact outer dimension, or at least, there is no overage. Not allowing for overage (the bottom panel extends out 1/6" or so in all directions prior to bonding) prevents a fillet from forming on the outer edge of the joint - the fillet prevent air from sucking into the joint.

The other pics seem to indicate an issue with edge prep. The prepped edge needs to be square and sharp, I'm guessing there is a bit of a round to these edges, or maybe an angle induced somewhere during the edge prep process. This results in a microscopic gap that shows up as the solvent evaporates.

This could also be related to the work surface. Acrylic panels will have variations in thickness, so to account for that you want a cushioned bonding surface/table so you can add shims after/during pinning and firm up the joint, and also so that you can put weight on top of the joint after pulling the pins and push it down a bit (and it generally does not take much overall weight, which is why I don't clamp joints)

Bubbles in joints on the inside can be fixed by adding a gusset. Gaps on the outer edge, there's not a whole lot you can do about that.

 

[Soup Sandwich]

The first pic: the bottom panel is rough sawn on the edge, telling me that it is cut to the exact outer dimension, or at least, there is no overage. Not allowing for overage (the bottom panel extends out 1/6" or so in all directions prior to bonding) prevents a fillet from forming on the outer edge of the joint - the fillet prevent air from sucking into the joint.

The other pics seem to indicate an issue with edge prep. The prepped edge needs to be square and sharp, I'm guessing there is a bit of a round to these edges, or maybe an angle induced somewhere during the edge prep process. This results in a microscopic gap that shows up as the solvent evaporates.

This could also be related to the work surface. Acrylic panels will have variations in thickness, so to account for that you want a cushioned bonding surface/table so you can add shims after/during pinning and firm up the joint, and also so that you can put weight on top of the joint after pulling the pins and push it down a bit (and it generally does not take much overall weight, which is why I don't clamp joints)

Bubbles in joints on the inside can be fixed by adding a gusset. Gaps on the outer edge, there's not a whole lot you can do about that.

Thank you very much for your reply. The bottom panel was 1/4 bigger than the lengths to allow for the overage. I had also used shims around the entire base to ensure for a tight seal. The problem occurred when I pulled the pins and snugged up the clamps. When doing this it caused a slight shift in the whole upper, I believe that is where the air crept in. I have since run a bead of Weldon 16 along the entire interior seam, in hopes to create a stronger bond. My the seam with bubbles on the upright can easily be the back of the tank, and the stand will include a piece of trim to cover the unsightly bottom seams. Cosmetically I am not worried, however I am concerned about the structural integrity

 

[Turbo's Aquatics]

On a tank that size, the weight of the tank alone should be enough, you shouldn't have needed clamps. Clamps force pressure and can lead to pushing out the melted acrylic mixture from the freshly set joint, as well as uneven pressure on joints. In your case, sliding (which you can control when it's just weights on top). It's better to just add 5-10 lb weights around the top of the tank. I've even used 12 packs of beer/pop.

 

[Soup Sandwich]

On a tank that size, the weight of the tank alone should be enough, you shouldn't have needed clamps. Clamps force pressure and can lead to pushing out the melted acrylic mixture from the freshly set joint, as well as uneven pressure on joints. In your case, sliding (which you can control when it's just weights on top). It's better to just add 5-10 lb weights around the top of the tank. I've even used 12 packs of beer/pop.

I like the sounds of that, only in my case they would just rapidly get lighter and lighter..

I had toyed with the idea of using just the weight of the tank but ultimately decided on bar clamps snuggly set all the way around.

95% of the tank is virtually seamless, these 3 areas are the only areas in the entire tank that have any sort of bubbles or air gap. Would you feel as though these areas would be grounds for concern moving forward, strictly from a structural concern?

 

[SteveMM62Reef]

You can Feather the Acrylic Edges with a Propane Torch for the smaller thickness Acrylic. For the Thicker Acrylic use MAP Gas. You use the side of the Flame, not the tip. Practice on Scraps. Also I recommend DuPont Teflon Dry Lube Spray for your cutting tools, to prevent Gumming. Clean the Plastic with Isopropyl before Solvent welding.

 

[lapin]

I like the sounds of that, only in my case they would just rapidly get lighter and lighter..

I had toyed with the idea of using just the weight of the tank but ultimately decided on bar clamps snuggly set all the way around.

95% of the tank is virtually seamless, these 3 areas are the only areas in the entire tank that have any sort of bubbles or air gap. Would you feel as though these areas would be grounds for concern moving forward, strictly from a structural concern?

I would use it. It is not perfect and thats how we learn to do better. I personally dont see the structural part being that bad. 1/2" with 24 inches tall is well within the outer limits. The logic for my decision: The side seam looks to have 1/8 the width compromised. Not too bad. Bubbles on bottom = air seeeeeeeeeeped back in as Turbo says

 

[Soup Sandwich]

I would use it. It is not perfect and thats how we learn to do better. I personally dont see the structural part being that bad. 1/2" with 24 inches tall is well within the outer limits. The logic for my decision: The side seam looks to have 1/8 the width compromised. Not too bad. Bubbles on bottom = air seeeeeeeeeeped back in as Turbo says

Excellent, thank you for your input. The Weldon 16 left a small bead when it cured as well, which makes me feel better about it. I will likely do that 1-2 more times around the circumference. The tank will have substrate and the stand will have mounding so it will not be seen.

...and I plan to let it run in the basement for a few weeks minimum just to be safe.

 

[Turbo's Aquatics]

let it cure for at least 2 weeks before setting it up. You can leak test after 48 hours or so, but the seams take time to cure - if you don't wait, they acrylic panels will absorb water slower than the seams, which can lead to the joints turning white and failing over time.

The rule of thumb is 1-2 weeks for 1/4", then add a week for every 1/8" of thickness. So technically if you want to be super safe, wait 3-4 weeks before putting water in it long term.

 

[Soup Sandwich]

let it cure for at least 2 weeks before setting it up. You can leak test after 48 hours or so, but the seams take time to cure - if you don't wait, they acrylic panels will absorb water slower than the seams, which can lead to the joints turning white and failing over time.

The rule of thumb is 1-2 weeks for 1/4", then add a week for every 1/8" of thickness. So technically if you want to be super safe, wait 3-4 weeks before putting water in it long term.

Okay awesome. It has been a week since I set the bottom and I still have all of the plumbing to drill and glue, and the sump to build.
Unfortunately over the weekend I wound up with 13 stitches in my arm and a decent part of my palm missing due to a slip while cutting some glass for the sump baffles. So waiting is most of all I can do for now. I will finish up when I can, and make sure it has been at least 3 weeks before I water test.
I really appreciate all your input!

 

[Justin_Reef]

Was there a post of section of posts on hand sanding/polishing edges? What is the best method? Best materials to use? What to be careful of? Ect.?

I have heard that even hand sanding and polishing can stress joints. Is that true?

 

[lapin]

Was there a post of section of posts on hand sanding/polishing edges? What is the best method? Best materials to use? What to be careful of? Ect.?

I have heard that even hand sanding and polishing can stress joints. Is that true?

You can remove the excess that you left for the fillet to form with a router and flush trim bit. This will leave a nice edge that can be polished. I use a sanding block with 1200 then 1800 then 2400 sand paper. Final polish is with Novis cleaner and an orbital buffer.
Sudden changes in temp and hot spots are not good for joints.

 

[Justin_Reef]

Thanks. All wet sanding?

What about storing a new acrylic tank in an unheated garage for a month? Temps here are usually above freezing. Had to convert from Celsius to Farenheit... average temp right now it about 46 in the day and then down to about 35 at night. I assume this is fine.