Aquarium cements must have 3 qualities - water resistance, adhesiveness, and elasticity, the latter to permit for the slight movement of the glass and frame because of their various coefficients of expansion. Don't use tough cement, simply because it's nearly impossible to remove, and this will make repairs extremely challenging.
A great high quality cement ready for use instantly is now obtainable in tubes and tins. This will, of course, save a fair quantity of time and trouble in mixing your own.
The very best high quality linseed putty is most likely the easiest to use. It ought to be well worked with the hands until fairly soft, and then liberally pressed into the frame with the fingers, taking particular care to fill the corners.
A slightly much better cement could be made in the event you mix two parts red lead, two parts white lead, and one component putty thoroughly, utilizing a little quantity of gold-size to unite the entire mass. To mix the leads with the putty use a board to lay them on, and maintain kneading the mixture with a broad putty knife.
Another easy cement is made from equal parts of white lead ground in oil and whiting. The lead and whiting are mixed together with the boiled linseed oil until it reaches the consistency of dough. This mass ought to then be hung in a muslin bag, a lot within the exact same manner as when making cream cheese, and left overnight to set. The next day it ought to be kneaded once more prior to utilizing. This particular cement has the virtue of remaining soft and in great condition for a considerable time if kept in an airtight tin, and offers a handy standby in an emergency. The more it's kneaded, the softer it becomes.
If it is essential to make fast drying cement, the following formula could be utilized:
Whiting - 16 parts
Litharge - 4 parts
Powdered red lead - 2 parts
Powdered resin - 2 parts
The ingredients ought to be mixed together with a great high quality varnish to the consistency of a stiff dough. If big areas are to be covered, don't make a big quantity at one time, but make it in little batches as needed to stop the unused cement becoming too tough to work.
Cement containing plaster of Paris ought to be avoided as it tends to dry rather brittle.