The yellowing is slight and normally occurs under intense UV lighting such as in a reef tank. I saw a tank a couple weeks ago over a decade old that was crystal clear. It was a freshwater tank and did not have the same lighting as a coral reef tank.
Weld-on #40 and #42
- Thread starter wednesday13
- Start date
I have a 300 gallon acrylic tank that I got a smoking deal on, it has a deep scratch on the front panel. I was curious if I could use the weld on 40 to fill the scratch then sand and buff. Also will be doing the tip and pour on all the corners, after buffing the whole tank. The tank holds water fine but you can never be to safe.
You should be able to sand and buff all the scratches out with a rubbing compound and buffer...If the scratch is extremely hanous yes the #40 will fill it in and buff out no prob. A lot more work with the 40 and it may make a mess if not careful, I'd def. try buffing the scratch out first before using #40.
Where is the scratch? Even if it's deep, work your way out further and further through the grits. Most scratches that are one inch by the time I'm done sanding are over 2 foot area. If its inside close to wall, ouch!! PITA!!!
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This was a great and informative read!!! Thanks to all of you who shared your knowledge. Is there a good technique to use to butt acrylic panels together length wise? How about just joining corners? I'm really curious about this product. I've only ever heard of weld-on #4. Where has #40 been all my life!!!
i used weld on 42 on a repair. how long before the fumes do not bother the fish? i was wondering if 24 hours is enough? this was a new sump that had tiny pin hole the leaked. it is time sensitive and if i can install in 24 hours, that would be great. but i am concerned about fumes or chemicalsr leaching into water. wondering what other people with experience thinks? it is a 150g saltwater tank, a 40 gallon sump, i plan to run carbon, small fix.
Id atleast wait 48hrs...the product takes a full 72hrs to cure in the first place so theres no use risking another pin hole leak and tear down to repair it again for not waiting a couple days. I usually wait up to a month when i do larger jobs but the last tank i did i waited around 7-10 days and filled it up no problem. Are you probably fine to fill it up in 24hrs. yes, nothing will leech out, but the repair will be alot stronger if you actually let it dry the full 72hrs or more 
. Whats the rush?
. Whats the rush?
This thread has me thinking, will the weld on 40 work well in resealing a glass aquarium? The tip and pour method seems ideal to seal one. Is there difficulty of this bonding to glass, as I know its definitely not the same as acrylic? Id like to trim out the old silicon in the interior of an old 125, and reseal. yet I worry if it wouldn't need total disassembly. Why is it that silicon is used with glass versus something stronger like epoxies?
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Im just gonna flat out say NO! Lol...solvents and epoxy are made for plastics and silicones are made for glass. Silicone already acts like the tip and pour method in a sense for glass so theres no difference and no logical reason to change this well practiced method. Not all silicones are created equal either, there are stonger adhesives/silicones out there for glass aquariums just the same. Silicone is used for glass because it sticks very well to it. #40 is used for acrylic because it sticks well. #40 on glass = no adhesion....just the same as silicone on acrylic = no adhesion. Cant change science lol...if u poured #40 on glass, it would simply dry and peel off with ur finger.
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