Best adhesive for glass to plastic and glass to glass

[mintakax]

I have some plastic Petri dishes with holes for small wells with glass cover slip bottoms. I would like to replace the cover slips myself. What might be the best adhesive for the plastic to glass bond ? I also have a second type of plastic dish where the bottom is complete covered with slip cover glass. To replace these I can only remove the glass around the hole, so the new cover slip would be glued to the remaining glass bottom so this would be a glass to glass bond. Would the same adhesive work for each ?

[janvangastel]

For glas -to glass silicone adhesive, the clear typ that smells like vinegar, works very well. It is used to glue fish tanks and is very strong. It might also work on plastic (I am not sure), but if it does you possibly need to use a primer.

[Hobbyst46]

I have some plastic Petri dishes with holes for small wells with glass cover slip bottoms. I would like to replace the cover slips myself. What might be the best adhesive for the plastic to glass bond ? I also have a second type of plastic dish where the bottom is complete covered with slip cover glass. To replace these I can only remove the glass around the hole, so the new cover slip would be glued to the remaining glass bottom so this would be a glass to glass bond. Would the same adhesive work for each ?

Here are some advices, by experience.
Assuming that the microscope is inverted so precious optics lie below the slide on the stage and should not suffer from leaks.

Commercial plastic petri dishes with coverslip bottoms are well made and do not leak. They are optically better than any DIY dishes, so I would try to recycle them as many times as possible. They can be cleaned with a solution of mild soap, or a very dilute solution of caustic soda (use eye and hand protective equipment), and or ethanol. Not acetone.

RTV, the vinegar-smelling silicon glue mentioned in the previous response, is a good sealant and will glue both glass to glass and glass to plastic. The challenge is to apply a very thin layer, such that will keep the coverslip parallel to the petri dish bottom, and still be leak proof. However, RTV is not resistant against ethanol.

Contact cements will work, but in this case, the above mentioned challenge is even more severe, and besides, they are poorly resistant against ethanol.

Cyanoacrylate glues, such as super glue, are not suitable, since they are not sealants. Also, they do not resist water well.

Norland 61 is an UV-curable glass to glass cement. It might bond glass to plastic as well, but I doubt its quality as sealant. It is fairly expensive, but can be purchased in 1ml packages that might suffice for a small batch of dishes.

Rapid action acetone- or other ketone- based glues, for example Duco cement, are inappropriate for polystyrene. Besides, they are not sealants AFAIK.

I have not tried Super-7, this is a wonderful cement that IMO will bond glass and plastic, so potentially good. It comes in transparent and white versions. It is a sealant. It is quite viscous, more than the previously mentioned adhesives. Again, the challenge is to apply a very thin uniform layer.

[tgss]

Depending on your intended use, if you decide to try silicone sealant, you should be careful about which type you use. Most sealants intended for household use, e.g. bathtub sealant etc., are compounded with antifungals, which can be harmful to living organisms. There are sealants made without these compounds which are considered safe for aquarium use, and one of these might be your best bet.
Cheers
Tom W.

[mintakax]

Thanks all for the advice -- I use the Commercial plastic petri dishes with coverslip bottoms dozens of times before its time to get a new one. I think they get slightly scratched over time. My main reason for gluing a new cover slip on a used dish, is that I want to use a #0 coverslip for the replacement. I've used two types of commercial dishes and the type that fits my carrier the best is not available with a #0 cover slip, only #1.5. The Apo objectives I am using have really short WDs and the #0 slips allow a little bit more depth before crashing into the bottom. I do not notice any optical differences between the #0 and #1.5s.

I tried CA glue and that did not work well. My wife is a glass artist and had a tube of Loctite glass glue. I tried it and so far it is working well with no leaks. I don't know if it will hold up. Any leaks will be a show stopper for sure !

[mintakax]

Depending on your intended use, if you decide to try silicone sealant, you should be careful about which type you use. Most sealants intended for household use, e.g. bathtub sealant etc., are compounded with antifungals, which can be harmful to living organisms. There are sealants made without these compounds which are considered safe for aquarium use, and one of these might be your best bet.
Cheers
Tom W.

Great point ! Thank you.