One with One without

[simplyweb]

Hello everybody , if we had two identical repairs but one had moisture in it, and one was dry how would they look different.Or do they look different

[Frank EU]

Hi SimplyWeb, it is not that I don't want to answer, but there is a recent topic started by yourself and it is called ''damp in a repair''.
I quote your question below;

How do you know if there is damp in a repair ,and what do you look for . I am just starting a repair business in the uk and it is always wet over here. Today I had a star break there was no way them legs would fill , could that of been damp.

There were some pretty good answers? It is just an idea, but why wouldn't you get a training screen (scrap yard, low price), build yourself a nice stand, create some bulls' eyes and get moisture in some? By the way; such a training screen is a wonderfull piece to play around with, heating, flexing, repairing cracks etc.

[maxryde]

Simply, yes they will look different. On inital inspection you may not see the moist one as different than the dry one. When in doubt dry it out!!. To know for sure if a chip is "wet" flexing will show the moisture that is present. Anyway it goes a drystar used properly will avoid problems.

Hello everybody , if we had two identical repairs but one had moisture in it, and one was dry how would they look different.Or do they look different

[simplyweb]

ye soz about starting this again i am just looking for a clear way of seeing the damp and what it looks like .with delamination you can see something ,you see a milky colour . I noticed if you use heat on a repair before you start , it visable shrinks ,is that because the damp as gone , or is it the heat closing the break up . But like you say just dry it anyway to be sure .

[Brent Deines]

If you heat the repair before you start and it visibly shrinks, it is due to the expanding glass. Moisture will typically make the break appear to be partially filled, so when the moisture is removed the break will be more visible with dark colored air spaces.

Although some will argue that the moisture can be removed by heating from the inside, that is simply not possible based on the testing we have done. If you use a moisture evaporator on the outside of the glass as recommended, the inside of the glass will only get warm, not hot. Therefore the same is true when you heat from the inside of the glass, so even if you use a vacuum on the outside to reduce the boiling point, you would still have to heat the inside of the glass to a dangerously high temperature to get the outside layer of glass hot enough to remove the moisture.

Anytime you remove moisture you should allow the glass to cool to the ambient temperature before proceeding, which generally only takes a couple of minutes as the heat quickly dissipates from the small area that is heated with a moisture evaporator. Allow more time to cool the glass if using a heat gun or torch to remove moisture.

[GlassStarz]

Im with Brent on this one
Maybe he could address one of the competitors beliefs that if you heat inside you dont need to get as hot because the steam vents out away from the heat and you have to get hotter on the outside because the venting is torward the heat source? didnt do that well in science but on the surface it made sence not sure if it works I quit heating on inside because its a pain to squeeze in there and both seem to work

[Brent Deines]

Water vapor or steam will come out the hole, which is on the outside of the glass; there is no other place for it to go. If you put a pin hole in the top of a sealed container and then heat it from the top that is where the steam comes out. Every time I show some of these myths to an engineer he just shakes his head.

It doesn't matter which side you heat it from except that if you heat from the inside, far more heat is required to get the same result because you have to heat the inner layer of glass and the PVB before any heat reaches the outer layer of glass. When you run your defrosters on the inside of the glass some heat will transfer through, but it can be hot to the touch on the inside and still quite cool on the outside on a cold winter day.

[simplyweb]

Thankyou for the great advice , this forum is fantastic the help and advice you all give is priceless .hopefully I will be around for ages like you boys and i to can give advice and share ideas with you all .

[Dave M]

This is the easiest example I can think of. You have 2 dime size bulls eyes, one with moisture present the other dry. The dry one will usually look completely dark, the wet one may look like a half moon dark. When using your drying out process on the wet one you should actually see the other half getting dark. This is when the moisture evaporates and air takes its place.

[Brent Deines]

My advice is to do your own test just as Dave M has described. Make two bullseyes on a windshield, put mirrors them, and spray one with water. That way you get to see what it looked like dry and full, or partially full, of water. Now dry it out. After the moisture has been completely removed with heat it will still look a little different than it did originally, but as it cools it will look like it did before you filled it with water. Having control bullseye next to it will help you to see the differences throughout the entire process.

If you are using a moisture evaporator in accordance to the MFG instructions, watch the mirror during the dry out process. Ten to fifteen seconds into the process you should start seeing some bubbling as the water boils and then evaporates. At twenty seconds you should no longer see any bubbling and the water should be gone. Regardless of the system used to remove the moisture you should be able to see the change happening, and a distinct difference in appearance when you are finished. If you can't tell if the moisture is being removed it probably isn't, at least with bullseyes and combo breaks. You should also see a change in star breaks, but as they contain less moisture to start with the change may be considerably less dramatic.