Curing under pressure

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Curing under pressure

Post by jdn » April 5th, 2019, 7:09 am

I see online there’s alot of people curing under pressure. They put the curing light right up against the injector. My question is what keeps the resin from curing at the injector tip or in the injector.

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Re: Curing under pressure

Post by kennycrane » April 5th, 2019, 1:46 pm

It apparently does not get the amount of uv rays that it needs to set up. I'm sure that if you left it long enough that it would set up, but while curing under pressure I will try and leave the light on it 2-3 minutes. Never had I had trouble with it harming my Delta tools.

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Re: Curing under pressure

Post by johnnyone » July 6th, 2019, 5:39 am

Why would you cure under pressure? This must be a new procedure?

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Re: Curing under pressure

Post by ghost rider » July 7th, 2019, 5:42 am

johnnyone wrote:
July 6th, 2019, 5:39 am
Why would you cure under pressure? This must be a new procedure?
Curing under pressure is not new. Some people cure under pressure because they can't or don't know how to remove all of the air and/or moisture from the damage. Pressure from the resin will force the damage to look filled by compressing it. I don't normally cure under pressure but i will admit I have done it a couple of times when I absolutely couldn't get whatever was in the damage to come out. Some UV has to get into the injector, I would recommend cleaning or changing injectors after curing under pressure.
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Re: Curing under pressure

Post by kennycrane » July 9th, 2019, 10:38 am

I don't know how many repairs that I have done but it is a bunch. Sometimes Its not that I don't know how to get the air out or the moisture, there are simply some breaks that you cannot get all of the air out so the only option is to cure under pressure (in my opinion). Its not cheating, it is not doing something wrong. It is simply making sure that the repair is repaired in the Best way possible.

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Re: Curing under pressure

Post by Glass Patch » August 8th, 2019, 8:45 am

Greetings
Curing under pressure was not common in the 1980's but not unheard of. When I was a Glass Saver, it was not a part of our practice but some of us did. Until I won a glasweld kit in a competition. I didn't have a UV light but found it useful and did some problem repairs under pressure. But I would work it back and forth and heat often before I used the UV under pressure.

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Re: Curing under pressure

Post by Dave M » August 10th, 2019, 4:11 am

I've been "curing" under pressure for 26 years. I have the light on two sides of injector for 30 seconds each, remove injector and do a full 5 minute cure. For me while under pressure the resin is forced to the end of cracks, what happens when you remove your injector? If all the air has been removed by the final pressure stage, what harm is curing under pressure doing?

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Re: Curing under pressure

Post by Jtmac » August 27th, 2019, 6:24 pm

I think the argument for curing under pressure claims that the resin shrinks when cured and it will eventually pull away from the break and the PVB if cured without pressure. Some air can also be reintroduced into the break when removing the injector before curing. These are not my words and may not be accurate but this is what my research has turned up.

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Re: Curing under pressure

Post by Brent Deines » August 28th, 2019, 2:25 pm

Jtmac wrote:
August 27th, 2019, 6:24 pm
I think the argument for curing under pressure claims that the resin shrinks when cured and it will eventually pull away from the break and the PVB if cured without pressure. Some air can also be reintroduced into the break when removing the injector before curing. These are not my words and may not be accurate but this is what my research has turned up.
I would argue exactly the opposite. Curing under pressure means there is pressure on the glass, which closes cracks, at least partially. You apply pressure on the inside of the glass to open a break, allowing more resin into the damage, especially cracks. So if you are applying pressure on the outside of the glass, and curing while in this state, when you remove the pressure you have more stress on the repair than if you removed the pressure prior to curing, which is in fact indicated by, in your words, "some air can also be reintroduced into the break when removing the injector before curing." That should not happen if the damage is filled properly and the injector is removed while still in the pressure cycle however.

Think about it this way. If you were filling a crack in a board with glue you would not push down on the crack while the glue was drying because it would squeeze all the glue out of the crack, making the bond less secure. If anything you apply a little pressure from the other side to open the crack up so you can get more glue in, then remove the pressure to allow the board to return to it's un-stressed state before allowing the glue to dry. The same principle applies to glass, metal, or anything else. It's always been interesting to me that no one in the wood working or metal working industry ever contests this simple principle, but in the windshield repair business, the debate never ends.
Brent Deines
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Re: Curing under pressure

Post by Jtmac » August 28th, 2019, 7:21 pm

If pressure on the glass closes cracks, then why do you flex a leg on a star break? It's to open it on the bottom and let the resin flow in more easily. A break in a windshield is not similar to a crack in wood as there is generally more damage or larger damage closer to the PVB or opposite the impact point. When you apply pressure from the outside of the windshield, most of that damage should be opening up. Likewise, when you apply pressure from the inside of the windshield on a crack that is through to the outside surface of the windshield, you are opening up the crack. Curing under pressure makes perfect sense to me for these reasons. Here's my analogy with the woodworking that is more accurately associated with glass. If the wood is cracked partially through and only visible on the bottom side but still intact on the top, how would you get the glue into the crack?? You would apply pressure to the top of the board, pushing down on the crack thus opening the bottom of the crack so you can get glue into it. The exact same thing happens when you flex a star leg. The 30-40 psi used to cure under pressure is not enough to distort the glass. It's kind of ironic you bring up woodworking. I've been teaching it since 1994 and doing repairs since 1998. I"m not meaning to be argumentative, but physics won't let me understand your stance that pressure on the glass closes breaks. I understand that head pressure may cause some legs to become tight but would you not agree that the damage is below the surface? If so, it has to open when pressure is applied from the other side.

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