# Optical Forums > Ophthalmic Optics >  Alloy vs. wax blocking?

## John J. Marcin

Hey, you lab wizards out there--give me some advice re: surfacing with wax vs. alloy blocking.  We run a small retail lab (lenscrafters-type), and are currently using alloy blocking.  My troops are lobbying for switching to wax, I guess 'cuz they're concerned about the lead, and/or they think wax is easier and less messy.  I heard it's easier to get lens warpage using wax (we use an Optek SL generator). Any input would be appreciated from the guys in the know.  Thanks!

----------


## AWTECH

I have provided a previous link regarding Lead and alloy.

I would stick with 117 alloy, and don't drink the water from the alloy tank, other than that precaution, I doubt that there are great health issues. 

http://www.optiboard.com/forums/show...ighlight=alloy

----------


## CDOT

Are your major concerns safety or are there other concerns? 

When switching from the old style coburn blocking (63/55mm chucks) Our breakage rate dropped massivley and lens quality improved drastically. But if you have updated technology (step one alloy/eclipse alloy) then i would stick with that as they are very consistent in regards to axis, prism and so forth.

----------


## Darryl Meister

> My troops are lobbying for switching to wax, I guess 'cuz they're concerned about the lead, and/or they think wax is easier and less messy. I heard it's easier to get lens warpage using wax (we use an Optek SL generator). Any input would be appreciated from the guys in the know. Thanks!


This would be a good one for Shanbaum to field. I will say that, in our experiments, wax blocking actually resulted in fewer blocking waves than alloy blocking. However, if you are AR coating the surface, the wax may leave a slight residue on the surface if it isn't cleaned properly (assuming that you're not using some form of surface protection prior to blocking).

----------


## CDOT

> This would be a good one for Shanbaum to field. I will say that, in our experiments, wax blocking actually resulted in fewer blocking waves than alloy blocking. However, if you are AR coating the surface, the wax may leave a slight residue on the surface if it isn't cleaned properly (assuming that you're not using some form of surface protection prior to blocking).


Darryl has a good point(doent he always?:p ) 

I was just at one of our AR labs we use and they stressed this point heavily.  Even with the best cleaning some wax is still present in the lens pores which can cause problems with adhesion

----------


## lensgrinder

You can get lead free alloy which makes it safer.  I had also heard that many wholesale labs were switching back to alloy due to the fact that it will hold the lens better and as Darryl said the AR factor.

----------


## Darryl Meister

Keep in mind that you can use surface saver tape with FreeBond blocking to prevent this issue (though I'm not sure if Gerber recommends against this practice); you'd have to use surface saver tape with alloy either way.

----------


## Jubilee

In the lab I used to work for, we actually did use surface saver tape with the wax. Much easier to clean :) Just make sure you compensate for the film thickness in the generator.


With wax, you can't "rush" the cooling of the lens. You have to let it cool at least 5 mins in order to get a good set and prevent deblocks. While I know it was recommended you do same for alloy, most places I worked didn't, and it was missed when the switch to wax occured. Especially when trying to do it all in 1 hour.;) 

With wax, it can get a bit messy. While you don't have a reclaim tank to worry about (and I knew people who worked wholesale that used to heat their cans of soup in the tanks!) the pulling off of wax, making sure the temp is just right that they peel off, and then getting those blocks clean can take some effot, unless you have a lens/block washer or the use of a crock pot. 

Cassandra

----------


## Leo Hadley Jr

I like wax because in the winter you can dip your hands into it and make disposable gloves, also you can make cool molds out of it or even use it to stick things too the wall instead of leap pads. 


Oh yea, its great for surfacing lenses too!!!:D

----------


## DPalmer

Having used both alloy and wax I think I would prefer to use wax although you still have to use blocking tape if your going to send your lenses for AR because of the whole wax getting in the pores of the lenses . Wax is much cheaper than alloy also .

----------


## shanbaum

The only significant objection to wax has been, as noted, the possibility of some wax residue remaining on the lens, which can adversely affect AR coating.  It's certainly OK to use tape to eliminate that problem, though thorough cleaning would probably be a better solution.

While neither material is ideal, were I to have to make a choice for my own lab, I'd choose wax over alloy in a heartbeat.

I'm not sufficiently familiar with the generator you're using to know if it produces some effects that would affect this choice.

----------


## hipoptical

A few considerations:
1. How much do you want to spend to upgrade? It is possible to use an automated blocker with wax or alloy. Good used units are available, but are likely to be wax only. A new system would give you the choice. 
2. Warping is not an issue with wax, but the need to let it cool properly is. 
3. Labs switch back to alloy because of old dogs and new tricks. 
4. Wax must be replaced after a period of time, but is relatively inexpensive. Alloy must be replaced when your lab "rats" have thrown too much away, taken too much home, spilled too much, etc., and it is slightly less expensive than a new car. 
I say do what you are comfortable with, but remember that your employees will either find a way to convince you to switch, or make your life a living (hot place full of pain and suffering). 
Better go with wax... :Rolleyes:

----------


## gola

I used alloid for many years. Two years ago we started with wax. GC Eclipse.

Faster and more accurate, many advantages. But has problems if wanted to re-surface a lens. Maybe the pressure that is applied to hold the lens while the wax is being inyected.
The thin lenses bend.
So now we have both systems to work with. Two machines with heating elements consuming electricity. So if you change to wax, keep the alloid just in case.
We has also notice that with wax we have more low power photocromic lenses (transitions and sunsensor) with aberration than when using alloid.

I have report this in other thread and has had sugestions as lower the pressure in the cylinder machine (already done) etc. The problem already exist. Now, we block those with alloyd too.

The SGX especially on Poly lenses, head the wax so much that it become sticky. I know that this is not normal and has not found th cause.
We wait at least 15minute to let the wax cool. We use on SGX the cutter that can be used with plastic, high index and poly. I do not know it that could be the cause.

We are waiting to receive a large generator in a few weeks from GC and hope this will do better.

Any suggestion is welcome.

----------


## PNKansas

I have experienced exactly what Gola has mentioned and completely agree :bbg: . You cannot expect to be able to resurface a lens very well if you have to reblock it with wax. You cannot expect to have a low powered Transitional lens come out very well either. Wax even in a clean invironment is highly messy. I have yet to see a clean Surface Dept. (no offense) that uses wax as a means for blocking lenses. The AR Adhesion which has been mentioned can create nightmares for the AR coating people cleaning the lenses in batches and not to mention the poor quality that you will have with adhesion.
You will (on average) experience more scratches due to having to use wax as well. Not from the actual wax, but the cleaning of the lenses that have wax "residue" still left on the lens that will need to be "rubbed" off after deblocking. A sales man trying to sell a wax blocker to you will suggest using tape as a means to seperate the wax from the lens thus keeping it cleaner...THIS IS A PIPE DREAM THAT DOESN'T WORK 100% :finger: . It is a hopeful idea if you are not grinding down Plus lenses into a small frame that wax wont get onto the lenses.

The other issue as mentioned is the price for Alloy is OUTRAGEOUSLY EXPENSIVE. Thanks to the technology industry. Other than minor health risks and a very high price Alloy is the way to go. 

However if by means of your team you change to wax DO NOT GET RID OF YOUR ALLOY BLOCKER you'll still have use for it. Don't retro fit it.

No matter what cutter you will use in the SGX generator it will "always" start to melt the wax when it gets to close to the edges of the blank or if the CT is getting to thin (even if you select for the rotation of the lens to slow down or speed up)....can you say "abberation waiting to happen" :Confused:  . Not to mention if you have to remove any excess wax that the fining/polishing pad will come into contact with. 

If you block with alloy all the SGX will do is shave it off 

Obviously I have very strong opinions about wax usage....YUCK!!:hammer:

----------


## chematech

> I like wax because in the winter you can dip your hands into it and make disposable gloves, also you can make cool molds out of it or even use it to stick things too the wall instead of leap pads. 
> 
> 
> Oh yea, its great for surfacing lenses too!!!:D


We can provide you SS tape for wax which will work clean with zero rejection.
anupam@chematech.net

----------


## chematech

We can provide you SS tape for wax which will work clean with zero rejection.
anupam@chematech.net

----------


## other_bill_fea

> We can provide you SS tape for wax which will work clean with zero rejection.
> anupam@chematech.net


You may want to reach out to him directly, as their need for tape for wax may have changed in the ten years since this was posted.

----------

