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Fri Dec 15, 2006 10:23 am  |
I've been doing a ton of research on sunblocks lately and have received so many great suggestions from members here at EDS - as a matter of fact, it was my initial quest for the perfect sunblock that led me to this wonderful forum so I'm very thankful for that! 
So now I'm a label readin' fool and I was curious about a couple things I just KNOW someone here will know!
1. Does the term sunblock refer to mineral based sun protection, and does screen refer to chemical base? I have seen these terms used interchangeably so I get confused 
2. And what determines SPF, anyway? Is the percentage of Titanium and Zinc oxide the primary factor in Sun Protection Factor?
How is this percentage calculated? If I see 10% Titanium Dioxide and 5% Zinc Oxide, are those percentages a ratio in relation to the rest of the ingredients in the bottle, or is this a ration in ppm or what?
3. Why don't all manufacturers include the percentage, don't they want us to know?
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44 – combo/oily skin with a tendency towards clogged pores. Thanks to EDS, tweaked my skincare routine and normalized skin… no more breakouts. PSF, silk powder, Janson Beckett, Cellbone, NIA24 are staples. |
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Fri Dec 15, 2006 1:16 pm |
Sunblock agents can be physical (mineral based; zinc or titanum) or chemical(oxybenzone, etc). I use the term sunblock loosely, because I'm not sure of any product that's going to block the sun completely. I typically use the word sunscreen. SPF is connected to mineral based agents and chemical. It can be either or. The SPF is also more connected to protection from uvb rays versus uva rays. The uva rays are connected to aging.
I also agree with you. I wish that most sunscreens would include the %'s of the sun protective agents. HTH |
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Fri Dec 15, 2006 2:07 pm |
| Does that mean if the percentage of titanium is higher, the SPF rating should be higher as well? |
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44 – combo/oily skin with a tendency towards clogged pores. Thanks to EDS, tweaked my skincare routine and normalized skin… no more breakouts. PSF, silk powder, Janson Beckett, Cellbone, NIA24 are staples. |
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Mon Dec 18, 2006 10:13 am |
"Does that mean if the percentage of titanium is higher, the SPF rating should be higher as well?"
Strangely enough, no. Often it's the actual formulation of base ingredients that affects SPF level, not just the percentage of active ingredients. It's not unusual for one product to have, say, 10% TiO2 and an SPF of 30 and for another to have 12% TiO2 and an SPF of 20. |
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Mon Dec 18, 2006 10:32 am |
paleface in my limited experience with titanium dioxide only sunscreens I would have to say that a 10% TiO2 sunscreen with a SPF of only 20 is unusual. It seems to me that give or take a few percentage points the SPF of a TiO2 only sunscreen is roughly 3 times the percentage of TiO2. So the other example you gave of 10% TiO2 and SPF 30 seems typical. I am very curious about this can you tell me what the SPF 20 sunscreen you mentioned is?
I wouldn't doubt that the base formulation could influence the SPF but IMO particle size (of the active mineral sunscreen ingredients) would influence the SPF more than base formulation. But I could be wrong here. Could you provide more information on how the base ingredients of a sunscreen influence SPF. TIA |
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Mon Dec 18, 2006 11:01 am |
Definition of "SPF":
The UV energy required to produce an MED on pretected skin divided by the UV energy required to produce an MED on unprotected skin, which may also be defined by the following ratio: SPF value = MED (protected skin (PS)/MED (unprotected skin (US)), where MED (PS) is the minimal erythema dose for protected skin after application of 2 milligrams per square centimeter of the final formulation of the sunscreen product, and MED (US) is the minimal erythema dose for unprotected skin, i.e., skin to which no sunscreen product has been applied. In effect, the SPF value is the reciprocal of the effective transmission of the product viewed as a UV radiation filter.
(in more simple terms, it is a measured ratio of the sun energy required to make the skin turn the characteristic red color of a burn when sunscreen is applied versus when it is not applied. Applying sunscreen will avoid this "erythema" longer by a factor know as SPF)
It should also be noted that an SPF value over 30 should be considered hardly any better than SPF 30. Scientific testing has proven that the benefit of these higher SPF value sunscreens is hardly measurable when compared to SPF 30.
The reason that manufacturers don't usually put the percent loading of the sunscreen materials is because they are considered "active" ingredients. These "active" ingredient sunscreens have upper limit load values set by the Sunscreen Monograph in the Federal Register. The manufacturers therefore don't have to put the load level on the label if they don't want to. But, you can tell for certain that they don't contain more than the following amounts:
Cinoxate up to 3%
Diethanolamine methoxycinnamate up to 10%
Digalloyl trioleate up to 5%
Dioxybenzone up to 3%
Ethyl 4-[bis(hydroxypropyl)] aminobenzoate up to 5%
Glyceryl aminobenzoate up to 3%
Homosalate up to 15%
Lawsone up to 0.25%
Menthyl anthranilate up to 5%
Octocrylene up to 10%
Octyl methoxycinnamate up to 7.5%
Octyl salicylate up to 5%
Oxybenzone up to 6%
Padimate O up to 8%
Phenylbenzimidazole sulfonic acid up to 4%
Red petrolatum up to 100%
Sulisobenzone up to 10%
Titanium dioxide up to 25%
Trolamine salicylate upt to 12%
(it is interesting to note that I didn't see Zinc Oxide listed in the Sunscreen Monograph. But, I did find it listed as a sunscreen agent in the CTFA dictionary).
paleface, you are absolutely correct that a different SPF value can be obtained from two formulas that have different ingredients yet the EXACT SAME loading of sunscreen actives. I have proven this by making four formulas with four different types of emollients in it, but all the same suncreen agents. It turns out that the emollient that "spreads" better by its physical nature helped to achieve a slightly higher SPF value than the lower spreading emollient formulas. This tends to make sense...the better the sunscreen is spread on your skin, the better the sunscreen agents can protect the skin.
John |
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President and Chief Formulator for "Never Over The Hill Cosmetics" |
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Mon Dec 18, 2006 11:05 am |
TheresaL, I also agree with paleface on the description of loading of TiO2 and ZnO related to SPF factor. I ofter "estimate" the SPF value of sunscreen formulas that I make by multiplying the loading % of TiO2 or ZnO by a factor of 2. Therefore, a formula with 10% TiO2 would have a rough estimate SPF value of 20. When I send these formulas out to have the SPF value determined by testing on skin, I often find that the value I estimated is very, very close to the value found in actual use.
Multiplying the loading by a factor of 3 is just too high.
John |
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President and Chief Formulator for "Never Over The Hill Cosmetics" |
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Mon Dec 18, 2006 11:22 am |
John,
I imagine that you have alot more experience with TiO2 sunscreens than I do but from personal experience I have found that the SPF listed on the bottle has been roughly 3 times the amount of the TiO2. I just double checked 2 of my sunscreens (Shiseido Sun Protection Foundation SPF 42 and Neutrogena Sensitive Skin Formula SPF 30) and found the ratio to be 3 to 1. Are you saying that by pure chance I happen to buy sunscreens that have a 3 to 1 ratio and not a 2 to 1 (BTW if you say yes I won't be shocked, I am a firm believer that we tend to underestimate coincidence). What would explain the fact that my sunscreens can have the same SPF with less TiO2? The formula or something else?
EDIT: I just wanted to add that in the above paragraph I am referring to sunscreens that use only TiO2 and have no other sunscreen actives.
Also, how big an influence would you say the formula has on the SPF for a given percentage of active sunscreen ingredients. I get the impression from your post above that it would make a difference but not a big difference. Is this correct?
Finally, what is your take on the particle size of TiO2 or ZnO effecting the SPF? My understanding is that the smaller the particle the more the protection is skewed toward the smaller wavelengths, so as particle size goes down you gain UVB protection at the expense of UVA protection. So smaller particle size would equal a higher SPF for a given percentage of the active ingredient. |
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Mon Dec 18, 2006 11:51 am |
TheresaL, I think you may have already answered my first question which would be...do these formulas have any other sunscreen active ingredients in them other than TiO2?
If not, then I suspect that it may be contributions from other ingredients that may be jacking up the SPF value in these products. It has been proven time and again that the better a sunscreen active is spread on the skin, the better it works. This is why almost every brand has you "repeat application often" and puts "spread completely over the skin" written on the labels somewhere.
In the study that I performed, I created a sunscreen formula that had 6% ethylhexyl methoxycinnamate, 1% butyl methoxydibenzoylmethane and 7% TiO2 in it. I made four versions of this formula, only changing one emollient in each.
Finsolv TN is the ingredient of choice for solvent effect on these sunscreen actives, so formula number 1 used this one. In formula number 2 I used "Floramac 10" from Floratech which has good solvent properties, and almost identical spreading properties to Finsolv TN. I like "Mac 10" better because of a much drier skin feel which makes the formula "non-greasy" feeling. I then worked with two new ingredients in versions 3 and 4 which have very high spreading properties.
Here is how the SPF values turned out in actual skin testing:
Version 1: 20.01
Version 2: 20.01
Version 3: 21.55
Version 4: 21.15
Notice how versions 1 and 2 have identical values, and the emollients in these formulas had almost identical spreading values as well. Notice also how the higher spreading raw materials boosted the SPF in version 3 and 4. You may also note that this increase is not by a huge amount, and I would suspect that to be the case most of the time.
So this phenomena can happen, and smart formulas can make better sunscreen formulas by using the correct emollients and spreading agents. Perhaps that is what is boosting the SPF value in the formulas you are referring to.
John |
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President and Chief Formulator for "Never Over The Hill Cosmetics" |
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Mon Dec 18, 2006 11:57 am |
By the way TheresaL, when I submitted these formulas for testing I "estimated" the SPF value to be 21.
7% TiO2 x 2 = 14
6% OMC x 1 = 6
1% Parsol 1789 x 1 = 1
Add the three together and get 21.
I was pretty darn close to the real value using this simple estimating formula. I multiply the loading of TiO2 and/or Zinc Oxide by a factor of 2. For all the organic sunscreens I multiple the loading level by a factor of 1, and then add all the ingredient's values together to get the estimated SPF.
Yes, particle size does play a role. The finer the particles size, the more even coverage can be obtained. Once again, this goes back to better coverage of the skin. "Micronized" powders are very fine in particles size and are often used in sunscreens. Also, the smaller the particle, the less "white" look you will get on the skin when you apply it.
John |
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President and Chief Formulator for "Never Over The Hill Cosmetics" |
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Mon Dec 18, 2006 12:00 pm |
John,
I did double check the formulas to make sure there were not other actives and they are both using only TiO2 so I guess the formula has something to do with it! In the case of the Shiseido foundation I imagine that some of the pigments and possible inclusion of iron oxides might be a factor....
BTW I am curious about something, what particle size (in nm) of TiO2 do you usually formulate with. And if you formulate with ZnO what particle size of that would you typically use?
Theresa |
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Mon Dec 18, 2006 12:05 pm |
I use specially made raw materials for sunscreen formulas. I like a product from Rona called Eusolex T-45D which is a blend containing fine particle size TiO2. I use Zinc Oxide from SunSmart that is called Z-Cote. I don't know the exact particle sizes of these materials but I bet they would be close to 1 micron which is extremely fine.
John |
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President and Chief Formulator for "Never Over The Hill Cosmetics" |
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Mon Dec 18, 2006 12:07 pm |
| TheresaL wrote: |
John,
I imagine that you have alot more experience with TiO2 sunscreens than I do but from personal experience I have found that the SPF listed on the bottle has been roughly 3 times the amount of the TiO2. I just double checked 2 of my sunscreens (Shiseido Sun Protection Foundation SPF 42 and Neutrogena Sensitive Skin Formula SPF 30) and found the ratio to be 3 to 1. Are you saying that by pure chance I happen to buy sunscreens that have a 3 to 1 ratio and not a 2 to 1 (BTW if you say yes I won't be shocked, I am a firm believer that we tend to underestimate coincidence). What would explain the fact that my sunscreens can have the same SPF with less TiO2? The formula or something else?
EDIT: I just wanted to add that in the above paragraph I am referring to sunscreens that use only TiO2 and have no other sunscreen actives.
Also, how big an influence would you say the formula has on the SPF for a given percentage of active sunscreen ingredients. I get the impression from your post above that it would make a difference but not a big difference. Is this correct?
Finally, what is your take on the particle size of TiO2 or ZnO effecting the SPF? My understanding is that the smaller the particle the more the protection is skewed toward the smaller wavelengths, so as particle size goes down you gain UVB protection at the expense of UVA protection. So smaller particle size would equal a higher SPF for a given percentage of the active ingredient. |
wow i love this kind of educational thread. Theresa, I checked my clinique city block spf 15, and found that it contains 5.3% titanium dioxide, so it is about 3 times as you said. |
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Mon Dec 18, 2006 12:38 pm |
| John C. Hill wrote: |
I use specially made raw materials for sunscreen formulas. I like a product from Rona called Eusolex T-45D which is a blend containing fine particle size TiO2. I use Zinc Oxide from SunSmart that is called Z-Cote. I don't know the exact particle sizes of these materials but I bet they would be close to 1 micron which is extremely fine.
John |
I have never heard of the Eusolex product (I looked it up but couldn't easily find any information!) but am familiar with Z-Cote. Actually BASF lists the average particle size for z-cote as less than 0.2 microns! I have read different information on this but from what I have read I would guess that Z-cote particles are about 100 nm to 150 nm and about the smallest size particle you would find in a batch of it is 70nm. If anyone can verify this, that would be great since the BASF listing of less than 0.2 microns is IMO sort of vague and I like specifics. 
gracedhy thanks for looking at your Clinique sunscreen. If I had anymore TiO2 only sunscreens laying around I would check those too because now I am very curious! |
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Mon Dec 18, 2006 1:37 pm |
| John C. Hill wrote: |
TheresaL, I also agree with paleface on the description of loading of TiO2 and ZnO related to SPF factor. I ofter "estimate" the SPF value of sunscreen formulas that I make by multiplying the loading % of TiO2 or ZnO by a factor of 2. Therefore, a formula with 10% TiO2 would have a rough estimate SPF value of 20. When I send these formulas out to have the SPF value determined by testing on skin, I often find that the value I estimated is very, very close to the value found in actual use.
Multiplying the loading by a factor of 3 is just too high.
John |
John and Teresa, thank you both for expanding upon this topic - forgive me if I'm not completely following this discussion completely, but I'm obviously still not understanding how this formula would work, unless you are both both be right about the contributions of active ingredient vs. formulation that applies to the SPF.
Ingredients for my sunscreen - Murad tinted spf 15. Multiplying 5.5% by either 2 or 3 don't come up to 15 - BTW is there any danger that a too small particle size would clog your pores?
Titanium Dioxide (5.5 %)
Water, Propylene Glycol Dicaprylate/Dicaprate, Butylene Glycol, Isodecyl Neopentanoate, DEA-Cetyl Phosphate, Glyceryl Stearate, Silica, Punica Granatum Extract, Chitosan Ascorbate, Zinc Aspartate, Lysine Lauroyl Methionate, Rice Amino Acids, Lecithin, Tocopherol, Magnesium Ascorbyl Phosphate, Sodium PCA, Retinyl Palmitate, Ascorbyl Palmitate, Palmitoyl Hydroxypropyltrimonium Amylopectin/Glycerin Crosspolymer, Vitis Vinifera (Grape) Seed Extract, Citrus Medica Limonum (Lemon) Peel Extract, Propylene Glycol, Cetyl Alcohol, Xanthan Gum, Acrylates/C10-30 Alkyl Acrylate Crosspolymer, Aluminum Hydroxide, Lauric Acid, Triethanolamine, Disodium EDTA Phenoxyethanol, Methylparaben, Propylparaben, Citrus Grandis (Grapefruit) Peel Oil, Citrus Aurantium Dulcis (Orange) Oil, Aniba Rosaeodora (Rosewood) Wood Oil, Geranium Maculatum Oil, Lavandula Angustifolia (Lavender) Oil, Thymus Vulgaris (Thyme) Oil, Iron Oxides (CI 77491, CI 77492, CI 77499), Talc (CI 77718) |
_________________
44 – combo/oily skin with a tendency towards clogged pores. Thanks to EDS, tweaked my skincare routine and normalized skin… no more breakouts. PSF, silk powder, Janson Beckett, Cellbone, NIA24 are staples. |
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Mon Dec 18, 2006 1:56 pm |
athena123 if you multiply the titanium dioxide in this sunscreen by 2.73 you get 15 so the factor in this case is not 2 or 3 but 2.73 (which is pretty close to 3 anyway!). I think the gist of what we are discussing is that there is no exact number that you can use to multiply the TiO2 with to arrive at the SPF. It will depend on other base ingredients in the formula and on the particle size of the acitve ingredients.
I have seen it mentioned on this forum as well as by Paula Begoun that mineral sunscreen ingredients can be pore clogging and cause acne. I like to stress the word can here because I think it depends on the individual. I have used zinc oxide sunscreens for a long time now and occasionally use ones that have some titanium dioxide and have never noticed that they caused clogged pores for me. But I do know that some individuals have problems with them. I honestly don't know if the particle size would matter when it comes to clogging pores. Hopefully someone else can answer that. |
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Mon Dec 18, 2006 2:06 pm |
Thanks Theresa - Yes, I've heard mineral sunscreens contribute to clogged pores but I've been using this one for the last 2 years without any problems, and it seems like the negatives with chemical sunscreens outweigh the positives.
Between Murad and mineral makeup I get adequate protection for winter but when I hit the beach this summer I am NOT going to wear makeup to go the beach! I want something strong enough that I can just slap on some sunblock, wear a floppy hat and go!
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44 – combo/oily skin with a tendency towards clogged pores. Thanks to EDS, tweaked my skincare routine and normalized skin… no more breakouts. PSF, silk powder, Janson Beckett, Cellbone, NIA24 are staples. |
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Mon Dec 18, 2006 2:07 pm |
There is only one true way of determining the SPF value for a formula and that is to do the skin testing with a large panel of volunteers and a calibrated UV light source.
The "mulitplication factor" method is just a way of getting a crude estimate for the SPF value. That's why I'm not surprised to see anything from a factor of 2 to a factor of 3 working for some of these formulas.
John |
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President and Chief Formulator for "Never Over The Hill Cosmetics" |
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Mon Dec 18, 2006 2:17 pm |
John,
Now you have me curious about something....
When a SPF is listed on a sunscreen is it always determined in the way you mentioned (by using volunteers) or are companies allowed to use other meathods to determine it?
Also, since this is technically not used in the US you may not know but when a sunscreen lists a PPD is that also determined in a lab using volunteers or do they use another meathod to calculate that? (BTW I actually am not sure if the Euro sunscreens list PPD values on their products or if this is something that retailers of the sunscreens and ambitious members of various skincare forums determine using the Ciba Sunscreen Calculator!)
Theresa |
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Mon Dec 18, 2006 2:24 pm |
I'll have to check on that for you Theresa, but I have a strong feeling that the SPF value is determined by actual skin testing of the product in question. There are many testing labs all across the US set up to do this type of panel testing.
John |
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President and Chief Formulator for "Never Over The Hill Cosmetics" |
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