Acrylic

[JeffDubya]

So... I bought some 1/4" acrylic from home depot with which I planned on building a sump. No, it wasn't the brand name "Acry-lite" but supposedly was just as good. The bigger sheets were $75 each so I figured just based on cost alone this must be some pretty good stuff.

So, I started to tinker. And even though it really wasn't a big deal from a construction perspective, my first project was a nice little lid with a handle for my 10 gallon tank housing my copepod culture. Turned out nice!

However, as several weeks have gone by, this acrylic is sagging. Or curling. Or both. At first, it just seemed like a curl, as the long ends of this lid both lifted. Significantly. Now, this thing is NOT a miniature half-pipe by any means, but if you held one side down flush, the other side is up by nearly 2 full cm. Now it also seems like the material may be sagging the other direction as well.

My first question is... did I do something wrong?

My second question is... I really don't want to be building a sump with this material, do I?

I really thought this material was pretty sturdy. I am in a little bit of shock about it. Now granted, this lid does not have any support bracing on it (that a sump would have) but it also is apparently not capable of sustaining its' own weight.

I'd appreciate your input.

[fat walrus]

You did not include braces in you lid design. It is normal for acrylic to "bow".

[JeffDubya]

even in a piece smaller than 10x20?

[thesaent14]

ok not all the acrilic is the same specialy from home depot is more flexible for some reason now you can build a sump but you have to make the bafels really tide and make a lit for it

btw

sorry for my spelling if you need any help just drop me a pm with youre number and ill help you beter

[JustDavidP]

Agreed! The sheer nature of acrylic is such that it will bow; even in small designs.

You do need to brace it somehow. I found, that when making lids, if you run a single strip of acrylic, centered down the entire length of the cover, it provides enough support to keep it from bowing.

Also, there ARE differences in brands and construction of acrylic products. When I'm simply making small "widgets", HD acrylic is fine. When making sumps, tanks etc. I order from a local company J. Freeman (Dorchester, MA) who is known for both high quality, and best selection of acrylic types.

Finally, when making tanks, sumps etc. don't skimp. My new pony tank is going to be 33X20X24 and is going to be thick, thick, thick. With that said, I am still going to "eurobrace" it.

Dave

[Amphibious]

Acrylic has a peculiar nature about it and most people are not aware of it and doubtful of this explanation when first heard. Acrylic absorbs moisture. Therefore the side of your lid that is toward the water absorbs water and expands and the upper dry side does not. This is causing the bowing you are experiencing. The way to avoid bowing from this phenomenon is, like Wally and David suggest, put a vertically glued brace lengthwise down the center.

A little more about Acrylic. First, Acrylic and Plexiglas are exactly the same thing "brand" named by two different companies that make it. Second, there are two grades of Acrylic/Plexiglas. Acrylic/Plexiglas comes in extruded and cell cast versions. Extruded is the cheapest and is less appropriate for aquariums but OK for sumps. It is softer and the surface has irregularities, sometimes visible to the trained eye. This is more likely what HD offers. Cell cast is cast in a finely machined mold and pressed under great pressure to give more rigidness, hardness to the surface and a finer finish. Cell cast is more scratch resistant and the preferred material for aquariums. Also costing more.

When making sumps and refugiums the cheaper extruded Acrylic is fine because any partition glued front to back will stiffen up the unit considerably.

When buying Acrylic aquariums, be wary of cheap prices from unknown manufacturers. At an IMAC show in Chicago a few years ago there was a truck load sale of really cheap Acrylic aquariums. Prices were unbeatable. But they sold few because it was obvious to many, not all, that something was wrong. The quality of workmanship wasn't there either and was obvious. I've never seen them back at subsequent IMACs. Buyer beware, you usually get what you pay for in this world.

When you are in the market for a new Acrylic aquarium, search for the best price and then question the manufacturer as to the type of Acrylic material used. The unfortunate thing is people will lie and most consumers cannot tell the difference, at first glance, between extruded and cell cast material.

Feel free to contact me for assistance on this matter. Or any other matter for that matter. That's a lot of matter, isn't it?

[JeffDubya]

I am told this is "cell cast" stock.

Regardless, thanks for the great information.

Now, my last question is - can I save the top I have? If I remove it from the tank will it return to shape? Or can I flip it and have it return to shape as the bottom side dries?

Thank you...

[JustDavidP]

I've been able to just flip them over..and watch until they get somewhat straight...and then brace them. You could also just put it in between something and let it settle out. It shouldn't have a "memory"

D

[Amphibious]

Originally Posted by JeffDubya

I am told this is "cell cast" stock.

Regardless, thanks for the great information.

Now, my last question is - can I save the top I have? If I remove it from the tank will it return to shape? Or can I flip it and have it return to shape as the bottom side dries?

Thank you...

If the protective paper was still on it, it would indicate whether or not it is cell cast.

And to answer your ??, yes.

[JeffDubya]

Originally Posted by Amphibious

If the protective paper was still on it, it would indicate whether or not it is cell cast.

I have more. I will investigate!