Not all caulking guns are equal when it comes to pushing caulk or adhesive through the nozzle.  Some caulks are very runny, while others are very thick.  Almost any gun will extrude the thinner caulks, but not every gun will push very thick contents out of a caulking tube with ease, or for that matter, at all.  It could be that you have experienced this and even drawn the conclusion that the contents of the tube have hardened.

 

Some manufacturers have addressed the problem created by caulks and adhesives that are very thick by providing guns with various thrust ratios.  So, what is a “thrust ratio”?  If you have a caulking gun with a 3:1 thrust ratio and apply 1lb of pressure at the trigger you, are applying 3lbs of pressure on the plunger of the caulking gun.  That will work fine for thin caulks and adhesives.  But what about the thick stuff?  Caulking guns are available with 6:1, 10:1, 18:1 thrust ratio and so on.  With 18:1 thrust ratio, one pound of pressure on the trigger exerts 18lbs on the caulking tube. At 18:1 you, have some leverage.  You can get guns with even greater ratios.

 

How do you know what thrust ratio you need when buying a caulking gun so you have the strength to push the material out of the nozzle?  It is unlikely the caulking tube indicates how thick its contents are.  Squeeze the tube:  If it is flexible, you can get by with the lower thrust ratios.  If the tube seems very stiff, the contents are likely very thick, so you will need to get a gun with a high gear ratio.

 

Another way to tell what type of gun to purchase is by knowing a product’s viscosity.  Water has a viscosity of 1cps at 75°F, you will have no trouble with water.  At 75°F degrees honey has a viscosity of 10,000 cps.  Some caulks and adhesives are at 250,00 - 500,000 cps, and most caulking guns will work with those products.   Liquid Nails is 500,000 cps.  Titebond Titegrab adhesive has a viscosity of 3,600,000 cps.  For Titebond Titegrab, you will need a gun with a thrust ratio from 18:1 – 25:1.

 

Trying to find viscosity on the label of a tube of caulk or adhesive can be difficult.  My suggestion is to keep the Gold Pro MGP3000 in your tool box.  With an 18:1 thrust ratio it can push most caulks through the nozzle.  If you want to step up a little buy the Franklin F17843 with a thrust ratio of 25:1. A thrust ratio of 10:1 or 12:1 is a good average.

 

The take away is this; don’t just buy any caulking gun.  Get one with a thrust ratio that matches the product you are extruding from the caulking gun.